The most potent opposition to President Slobodan Milosevic has emerged not in Belgrade, the capital, but in provincial Serbian cities where dissident mayors and local officials say they can topple the Yugoslav leader. But they need help from the West, they say, and now.

They don't want guns. They want bridges. And transmitters, cement, transformers, ferries and, most important, oil and diesel fuel to keep their citizens from freezing next winter.

"You Americans want to get rid of Milosevic? So do we," said Nenad Canak, a leader of the League of Social Democrats here in Novi Sad, a Danube River city 50 miles northwest of Belgrade. "You get me a bridge."

By this, Canak and other urban opposition leaders mean they need to show voters that the West does not hate them and that they do not need Milosevic to rebuild their bombed-out bridges and ruined economy, in which average salaries have plummeted to about $50 a month.

But the United States and other NATO nations have declared that, while they will provide humanitarian aid to Serbia--the dominant Yugoslav republic--they will not spend any money rebuilding its bomb-blasted infrastructure as long as Milosevic remains president of the Yugoslav federation, which also comprises Serbia's disaffected sister republic, Montenegro.

Canak, and the mayors of some of the largest cities in Serbia, say the West is missing an opportunity to challenge Milosevic. Seven years of sanctions did not work, but "strategic help" could, they say, and the West should find a way to funnel money directly to opposition-run cities--through humanitarian groups, Montenegrin banks or simply by sending materials.

"I'm thinking of something like a sister cities program," said Zoran Zivkovic, the mayor of Nis, another major Serbian city 120 miles southeast of Belgrade, capital of both Serbia and Yugoslavia. Zivkovic has a list of what he wants. At the top is 20,000 tons of heating oil. Without it, about a third of his city--90,000 residents who rely on "remote heat" from city steam plants--will have to do without. He estimates the heating oil would cost about $1 million.

Zivkovic said that since NATO spent about $50 million a day to bomb Serbia, "this is a reasonable request." He suggested that some U.S. or European city could donate it. It would be a lifesaver, Zivkovic says, and a powerful political tool.

Goran Matic, a government minister close to Milosevic, called the opposition scheme "pure stupidity" and an attempt by the West to blackmail Serbia with offers of aid if only the people would remove Milosevic. The opposition leaders are dreaming, he added, if they really believe the West will help them.

Just as in the United States, where local politicians can amass power and support by mending potholes, the opposition here wants to prove that the West supports those who question Milosevic. "We're not asking for help ousting him, that is our job," said Vuk Obradovic, a former Yugoslav army general and now leader of a small opposition party. "But we need to show the people something real, something they can see with their own eyes."

Ognjen Pribicevic, a strategist with the opposition Serbian Renewal Movement, was more straightforward: "We can't rebuild the country with shovels and slogans. We need foreign money and investment. Lots of it. The longer we remain in a cage, the worse for us."

Milan S. Protic, an intellectual who also wants to see Milosevic removed, said city halls around Serbia have tremendous power. "These people made a difference under most difficult times, and they're going to win again," he said. "The West should show them a sign."

The NATO alliance and much of the Western media have often portrayed Serbia as united in antipathy toward the West. But most of its major cities--including Belgrade, Novi Sad, Nis, Cacak, Kraljevo and Kragujevac--are run by opposition parties that are calling for the resignation of Milosevic, creation of a transitional Yugoslav government and new elections. Mass rallies and other anti-Milosevic demonstrations have already taken place.

The pro-Milosevic Serbian president, Milan Milutinovic, was booed when he appeared in the town of Kursumlija last week. Over the weekend, about 500 army reservists blocked roads outside Raska, demanding back pay. And in Leskovac Sunday, a producer at the local TV station locked himself in the studio during the broadcast of the Yugoslav-German basketball game and urged the resignation of the district administrator, a member of Milosevic's Socialist Party. On Monday, thousands of chanting protesters took to the streets of Leskovac to support the technician.

Milosevic has been calling for national unity on reconstruction and is promising, for example, to rebuild a bombed Novi Sad bridge in the next 30 days. But Canak and his allies want to beat him to the punch--and snatch the credit. Forgoing the stiff rhetoric of some of his more academic colleagues, Canak sat one recent night at Novi Sad city hall, dreaming of his bridge. He said he was promised about $10 million--by "people in Vienna, and I can't say exactly who"--and a team of Austrian engineers to build a temporary bridge.

At a rally in Novi Sad Friday, Canak told several thousand protesters that the engineers were denied visas by the Milosevic government. The crowd hooted, whistled and chanted: "Dump Milosevic!"

The opposition mayors and leaders say they do not think their citizens would begrudge assistance from the countries routinely dubbed "the NATO aggressors" in state media. "All our cities were bombed, especially the cities where the opposition is greatest," said Zivkovic, the mayor of Nis. "Now, how do you explain to the people who voted for democratic reforms, who rallied against Milosevic, how do you explain that, well, the Western democracies bombed and killed you, and now they don't want to help you rebuild?"