WASHINGTON (AP) - In a summit-ending show of solidarity, NATO leaders promised military protection and economic aid to Yugoslavia's neighbors for standing with the West against Slobodan Milosevic. "If Mr. Milosevic threatens them for helping us, we will respond," President Clinton promised.

Before winding up the meeting with his allies, Clinton telephoned Boris Yeltsin yesterday and urged the Russian leader to press Milosevic to accept a peaceful solution.

"There has been this breathtaking explosion of freedom, but the old order has not yet been replaced by a new one," Clinton said, summarizing the position of the alliance as it begins its second half-century.

NATO's 19 members agreed to move toward an oil embargo to hinder Milosevic's war machine despite Russian objections and French misgivings over forcibly searching ships at sea. The leaders agreed to intensify the air attacks designed to force the Serbs to allow 1.4 million ethnic Albanians to return to their homes under international protection. But there was no agreement - and scant public discussion - of the possibility of introducing ground forces.

Clinton said the world one day would see as historic a summit during which the leaders agreed to expand NATO's shield. "We have reaffirmed our readiness ... to address regional and ethnic conflicts beyond the territory of NATO members," he said.

In one of their final acts, NATO's leaders sat down with the representatives of the "frontline states" - Yugoslavia's seven neighbors, all feeling the fallout from the combat - and promised to stand by them.

"The nations of the region have risked, and even faced, armed confrontation with Serbia by facilitating and supporting our campaign to end the bloodshed in Kosovo," Clinton said.

Albania and Macedonia have been particularly hard hit, taking in nearly 500,000 Kosovar Albanian refugees fleeing from Yugoslav military action. The other neighboring countries are Bosnia, Bulgaria, Croatia, Romania and Slovenia.

"They need help and we are giving it to them," NATO spokesman Jamie Shea said. "We will not tolerate threats against them or attacks on them by Belgrade."

Summing up the three-day meeting, NATO Secretary-General Javier Solana said, "The most important message that you are going to get from this summit is the determination of all the allies and all the partners to reverse the situation in Kosovo.

"The refugees are going to be back in their place, in their country, and ethnic cleansing will not be victorious in our continent as we approach the 21st century," Solana said.

Clinton and Yeltsin talked for nearly an hour by phone. Russia has expressed outrage about NATO's airstrikes in Yugoslavia and has threatened to ignore a Western oil embargo. Yeltsin briefed Clinton on former Prime Minister Viktor Chernomyrdin's mediation efforts in Belgrade, which NATO officials say have failed to produce results warranting a halt to the bombing.