KILINOCHCHI, Sri Lanka -- Three weeks ago, Suren Sornalingam was managing logistics for Nike Inc.'s European operations from his office in Amsterdam. Now, he's running relief convoys in Sri Lanka -- to a region controlled by separatist guerrillas known as the Tamil Tigers.

Standing in a cramped warehouse on a recent evening, Mr. Sornalingam, 37 years old, organized a shipment of rice, sardines and water tanks for hundreds of thousands of ethnic Tamils whose homes were washed away by the Dec. 26 tsunami. Hours later, he boarded a van for a 10-hour journey to Sri Lanka's northeast. He wanted to make sure the relief reached his fellow Tamils, a Hindu minority in this predominantly Buddhist nation of 17 million.

"Unfortunately, the government has always treated the Tamils as second-class citizens," Mr. Sornalingam says. "We've had to take the initiative to make sure our people recover."

Ethnic Tamils from around the world are mobilizing to respond to Sri Lanka's humanitarian crisis. Yet the speed and success with which the Tamil diaspora has acted also presents an unusual political risk for the country.

That's because the outpouring of support for Tamils could affect a tenuous truce between the government and a Tamil rebel group that has been waging a decades-long civil war. The rebels, called the Liberation Tigers of Tamil Eelam, are considered a terrorist group by the U.S. government.

Some Sri Lankan government officials say the efforts of Tamils in other nations -- working largely through the Tamils' chief humanitarian-aid agency -- could steel the rebels' resolve. Tamils want to manage their own relief efforts "because it promotes their efforts to secure autonomy," says Wimal Weerawansa, a parliamentarian with the People's Liberation Front, a partner in Sri Lanka's ruling coalition.

Sri Lanka's civil war has been one of the world's most brutal, costing some 65,000 lives and splitting the country in two. Outside Sri Lanka, the Tamil Tigers are perhaps best known for suicide bombings, done in hopes of furthering their quest for an independent state. Tamil Tiger insurgents in effect control parts of Sri Lanka's northeast, and have their own navy, judicial system and more than 5,000 soldiers.

Initially, there was hope the enormity of Sri Lanka's disaster could give fresh impetus to the peace process. Both sides' navies sustained significant losses from the tsunami, military analysts say, and there have been incidents of Tiger troops cooperating with government forces in relief operations.

But political tensions around tsunami aid are emerging. Sri Lankan President Chandrika Kumarantunga -- who lost an eye to a Tiger grenade in 1999 -- was photographed shaking hands with rebel commanders in local newspapers soon after the tsunami.

On Saturday, however, Ms. Kumarantunga's government nixed an invitation from the Tigers to United Nations Secretary General Kofi Annan to visit devastated Tamil districts. That touched off Tamil protests and prompted a diplomatic scolding from Mr. Annan."The U.N. is not here to take sides," he said.

Leaders of the insurgency say aid earmarked for them is being redirected to the majority Sinhalese population in the south -- a charge the Sri Lankan government denies. In fact, the president, Ms. Kumarantunga, and other government officials say the country is sending more aid to the north and east, where most of Sri Lanka's two million Tamils live.

Tamil expatriates' relief efforts are being coordinated through an agency called the Tamils Rehabilitation Organization. The TRO has offices in 14 countries, including the United Kingdom, Switzerland, Australia and the U.S. The TRO also oversees hundreds of medical clinics, schools and camps in Tamil communities in Sri Lanka -- many in areas controlled by the rebel Tigers.

Following the Sept. 11, 2001, attacks on the U.S., the Bush administration placed the Tamil Tigers on its list of terrorist organizations, citing their use of suicide bombers and political assassinations.

The terrorist designation bans the U.S. and international agencies from supplying cash or aid to the Tamil Tigers. The TRO, as a result, will need to show that every water bottle and bowl of rice it distributes is going directly to refugees -- rather than rebels -- if it wants to keep its status as a nongovernment organization. The U.S. Treasury Department's Office of Terrorism and Financial Intelligence is closely watching tsunami-relief operations, including TRO's work with the Tigers, people familiar with the matter said. The TRO says it is purely an aid organization, independent of the Tigers. The group says it will continue its efforts to deliver aid regardless of scrutiny.

"We simply don't have time to debate at this time," says Chandru Para-rajasingham, an Australian national who heads the TRO's office in the Sri Lankan capital of Colombo. "There are too many lives at stake."

There are more than one million Tamils living overseas who consider Sri Lanka their original home. Many left because they felt the government discriminated against them, on racial and religious grounds. There are tens of millions more Tamils in India and other countries.

The Tamil diaspora network has helped the TRO execute one of the most effective tsunami-relief operations in Sri Lanka, say aid agencies and government officials. The TRO has deployed more than a dozen medical teams and scores of truckloads of supplies. It has raised more than $2 million.

Roughly two-thirds of the 30,000 fatalities in Sri Lanka are reported to be from the country's north and east, traditional Tamil homelands. Aid groups warn the numbers could rise sharply if shelter, food and water aren't delivered quickly.

The TRO was born in 1985, two years after anti-Tamil rioting broke out across Sri Lanka. Tamils fled to southern India during those years, as well as to Western countries. Tamil leaders moved to establish an international group to support their displaced communities.

The organization set up offices and welfare centers inside Sri Lanka during the mid-1990s, when fighting between the Tamil Tigers and the Sri Lankan army drove hundreds of thousands of Tamils into refugee camps.

Today the TRO operates extensively inside Tamil Tiger-controlled areas. "It's true we have to work alongside the Tigers to operate in these areas. We don't deny that," says Mr. Para-rajasingham, of the TRO. "But if we didn't, we couldn't help any of the people here."

The Tigers run virtually every facet of life in districts under their control. They extract sales taxes and run their own police and judicial systems. Visitors must cross a carefully monitored series of checkpoints.

The trust developed between the Tamil Tigers and the TRO has proven key for tsunami victims. Within hours of the calamity, TRO offices in Tiger territory and in Colombo began relaying damage assessments. Offices from overseas began sending money and supplies. Tamil communities in Australia held telethons and raffles.

"The tsunami has pulled the Tamil community together more than ever before," says Mr. Para-rajasingham.

The TRO's two-story office in Colombo has become the group's command center for relief efforts. On a recent day, Mr. Sornalingam, the Nike executive, mixed with dozens of expatriate Tamils as wells as non- Tamil Norwegian, American and Australian volunteers.

In a conference room dubbed "the hub," volunteers logged onto 12 personal computers and typed out aid requests to present to foreign governments. Others updated casualty figures on the TRO's Web site and sought donations. In an adjacent office, volunteers tried to match medical requests from the refugee camps with supplies the TRO has collected.

"It's all a bit chaotic, but it somehow seems to be working," said Amalan Kanagaratnam, a lawyer from Los Angeles who was visiting family in Sri Lanka when the tsunami hit. Within hours, the 30-year-old was helping aid workers deliver food and medicine.

"It was just terrible what I saw," says a shaken Mr. Kanagaratnam, a U.S. citizen who is an ethnic Tamil.

Australian Durga Owen, 21, loaded boxes of relief supplies onto TRO trucks on Friday and grumbled about the government's response to the crisis. "Our job is to make sure that aid is being delivered," the gangly law student said.

Volunteers in the TRO office say the most pressing work is in the more than 200 refugee camps the organization helps administer.

At one of the camps, in a town called Pallai, the TRO oversees efforts of international aid agencies now making their way into the area. Officials from Unicef consult with TRO officials on how to best administer a new delivery of medicine.

"This way the international agencies can hit the ground running," says Geodhini Sivaraj, who heads the TRO's Sydney office. "They don't have to reinvent the wheel each time."

Last Wednesday, the TRO managed to get refugees to prepare their own food for the first time since the disaster, a lunch of rice and lentils. Children handed battered metal plates of food to visitors.

"This is one of the most organized relief efforts I've seen," says Dharitri Patnait, an Indian aid specialist at Bangalore-based ActionAsia International. "I think it's because they are used to dealing with displaced people because of the war."

The Tigers play an important role in channeling aid into territory they control.

At a checkpoint in the town of Oranthai, most vehicles are subject to the Tigers' stringent inspections. Some wait overnight for their turn to enter the rebel-controlled area, with drivers setting up hammocks or sleeping in their trucks. But clearly marked aid vehicles are swiftly led through barbed-wire barriers with an escort of the Tigers' own blue-uniformed police motorcyclists, sirens blaring.

Some aid recipients don't distinguish between the Tigers and the TRO. P. Rajendran, a fisherman, says he had to flee his home in the mid-1990s because of skirmishes between the Tigers and Sri Lankan troops. After a spell in a refugee camp, he says the TRO helped him find a new place to live further down the coast.

He lost a young son in the tsunami. But he speaks with pride about the Tamil community's sense of self-reliance. "We can't rely on the government to help us," he says. "We know how to take care of ourselves."

It is precisely this brand of thinking that's creating growing tension between the government and the Tamil Tigers, often with the TRO in the middle.

Since the government and the Tamil Tigers agreed to a cease-fire in February 2002, violence in the country has subsided substantially. That's a big reason foreign tourists were returning to the country's beaches and tea plantations.

Now there are signs Sri Lanka's recovery efforts are falling victim to its ethnic and political divide. The guerrillas' invitation to the U.N.'s Mr. Annan was particularly vexing to the government.

"At a later date, the [Tamil Tigers] are likely to make representations to the U.N. that they already have self rule in the north and east as part of a bid for recognition as a separate state," JVP general secretary Tilvin Silva wrote last week to parliament's opposition leader.

The TRO's efforts are falling under new restrictions. In the days immediately after the tsunami, volunteers were able to secure aid directly from some foreign governments, the TRO says.

The Sri Lankan government, however, now wants to control aid coming into the country. President Kumarantunga established three task forces last week to coordinate the aid effort. Her government requires all international donations be channeled through central-government agencies, rather than independent outfits like the TRO.

"We have a more formal structure now. It's more organized," says Tara de Mel, who heads the government's Task Force for Rescue and Relief. "We now have committees for each camp, which are working closely with the military."