With the flick of a match and fuel from an oily rag, one of five aging generators was up and humming here today at Kosovo's main power plant, promising the first supply of reliable electricity since the end of the war.

But the problems encountered by NATO forces in restarting the coal-fired plant--not to mention lingering doubts about how long the Communist-era relic will hold out--illustrate just how difficult it will be to rebuild this rubble-strewn province and bring together its ethnic Albanian and Serbian communities.

The assembly of a joint work force of 600 ethnic Albanians and 250 Serbs has been marred by periodic threats and harassment from both sides, NATO officials said, and workers say the two groups try to avoid each other as much as possible.

Ethnic Albanians grumble that NATO's efforts, which have focused on building a multiethnic work force, have allowed too many Serbs to hold well-paying jobs.

Employees on both sides predict that the Serbs, who held more jobs and privileges than did ethnic Albanians before the war, will leave once NATO troops stop overseeing security.

Many Albanians were fired from the plant a decade ago, when the Belgrade government stripped the ethnic Albanian-majority province of autonomy and installed local Serbs in most key positions.

"We can't cooperate with them," said Miftar Mehani, 37, an ethnic Albanian electrical technician who has worked at the plant for a decade. "We are still seeing the horrors, and there are people who I work with who were part of that. . . . There's nothing for them here now."

The 36-year-old power plant is a mess, a casualty of years of neglect, but NATO officials insist it will provide for Kosovo's near-term electrical needs until a more modern plant can be reopened nearby.

But several workers said the older plant desperately needs major upgrades, both to modernize equipment and correct shoddy repairs and lax maintenance. The boilers that power the generators are patched, employees said, and spare parts were spirited away long ago.

Officials say it will take weeks before the plant is operating at capacity.

Then there is the problem of pollution. Zoran Stanisavlievic, an engineer, said that each of the plant's towering smokestacks emits 20 tons of acidic coal ash per hour, sending up a gray-brown plume that frequently blankets nearby Pristina, the Kosovo capital, in the wintertime. "I will give it maybe 10 days," said Ingsabit Hyseni, 45, who oversees one of the plant's control rooms. "It's very unstable, and we are working it very hard. The whole electrical grid is very damaged."

Nearly a third of Kosovo's people have no power, including more than half the residents and businesses in the hard-hit western part of the province, according to Col. Max Heron of the British Royal Engineers.

Both neglect and NATO's 78-day bombing campaign badly damaged the electrical "supergrid" that covers Kosovo, forcing officials to rely on local grids for power.

Most heavy industry here has been shut down for weeks or months, and a lack of power has been a major obstacle to getting it restarted. Pristina and other urban centers have also had to contend with regular electrical and water outages since NATO ended its bombing campaign five weeks ago.

With its one operating generator and electricity imported from nearby countries, Kosovo now has the minimal amount of power it requires, officials said.

With winter looming, maintaining and increasing that capacity will be vital.

"In the last 24 hours, we have effectively doubled the power available in Kosovo," Heron said, standing in sight of an aging plaque extolling Tito, who founded communist Yugoslavia in 1945. "Quite clearly, restoration of power is one of the main objectives. . . . The first thing we have to do is get people back to work."

Heron and other NATO officials said the plant's management eventually will be turned over to the U.N. agency responsible for rebuilding the province. British troops will continue to guard against sabotage or conflicts between workers in the near term, officials said.