NEWS ANALYSIS : Ukraine Accord Rests on Hope, Not Confidence : Arms: Pact relies heavily on Kravchuk’s assurance he can deliver despite opposition in his Parliament.

The agreement announced by President Clinton to peacefully dismantle Ukraine’s huge nuclear arsenal will be a diplomatic triumph for both Russia and the United States--if it works.

But no one, including the U.S. officials who negotiated it, is sure that it will.

The agreement would erase the world’s third-largest nuclear arsenal, more than 1,800 warheads that posed a long-term threat to Russia, the United States and much of Europe.

But whether Ukraine actually carries out the deal rests on hope more than confidence.

At this point, the pact includes no timetable that commits Ukraine to giving up its weapons by a specific final deadline. And it relies heavily on the personal assurance of one man, Ukrainian President Leonid Kravchuk, that he can deliver it despite determined opposition from the nationalists who form a majority in his Parliament.

“The United States has brokered a good deal in which everybody wins,” said Bruce Blair, a nuclear weapons expert at Washington’s Brookings Institution. “It is premature to celebrate, however. Ukraine in particular has signed agreements along these lines before--and has broken the promises.”

U.S. officials acknowledge those problems but argue that this is one case in which an imperfect agreement is better than no agreement at all.

“What’s important is that we get a process going,” said a senior State Department official who helped negotiate the pact. U.S. officials argue that once Ukraine begins dismantling nuclear weapons--and begins collecting more Western economic aid in return--sentiment in Kiev will swing toward continuing the job.

The three-way agreement, which Clinton, Kravchuk and Russian President Boris N. Yeltsin are to sign in Moscow on Friday, requires Ukraine formally to “eliminate” all nuclear weapons on its territory.

In return, Ukraine will receive nuclear fuel for its civilian power plants, debt relief from Russia, a promise of new economic aid from the United States and renewed security assurances from both big powers.

The nuclear fuel, worth about $1 billion, will represent the energy equivalent of the weapons-grade uranium that Kiev is giving up. Under the pact, Ukraine’s warheads will be shipped to Siberia, where Russian technicians will extract the highly enriched uranium and turn it into less powerful civilian reactor fuel.

The pact could also lead to a doubling of U.S. economic aid to Ukraine, from $155 million this year to $310 million, the White House said. The United States has also offered at least $175 million to help pay the actual cost of dismantling the nuclear weapons.

If Ukraine fails to keep its promises, officials noted, the Administration could respond by withholding much of that aid.

As for security assurances, the United States and Russia will declare their respect for Ukraine’s existing borders and its right to independence from military or economic coercion. Russia’s declaration of respect for Ukraine’s borders is intended in part to meet a longstanding Ukrainian concern: the demand of Russian nationalists for the return of the Crimean Peninsula, which was Russian territory before it was transferred to Ukraine in 1954. Nevertheless, Ukrainian nationalists in Kiev lost no time in attacking the pact on Monday night.

“This is an economic crime, because we’re giving away pure gold and getting back ore,” complained Yuri Kostenko, Ukraine’s environmental minister and deputy chairman of the Parliament’s disarmament commission.

Kostenko, a member of the majority that largely supports Kravchuk, predicted that the Parliament will demand the right to approve or disapprove the agreement--a process that could leave the pact in limbo for months.

To make life easier for Kravchuk, U.S. negotiators agreed to leave two key parts of the pact ambiguous, according to officials traveling with Clinton to the summit of the North Atlantic Treaty Organization in Brussels.

One is the timetable. The pact does not fix a specific final deadline, because Kravchuk warned that it might anger the Parliament, one official said. Instead, it recommits Ukraine to observing the 1991 Strategic Arms Reduction Treaty, which has a seven-year term--but even that deadline is not mentioned explicitly.

The other is the U.S. demand that Ukraine move quickly to dismantle its most dangerous nuclear weapons, 46 long-range SS-24 missiles. Some Ukrainian nationalists want to keep the SS-24s as long as possible. So the pact does not mention the SS-24s but includes a less specific commitment to eliminate “the most dangerous weapons” first, an official said.

The pact could cause trouble for Yeltsin in Russia’s new Parliament as well. “The growing voices of nationalism in Russia will resist relinquishing Russian claims on the Crimea, perhaps even on all of Ukraine,” noted Blair, citing the strength of ultra-nationalist leader Vladimir V. Zhirinovsky in Russia’s parliamentary election last month.

U.S. officials have been trying to pin Ukraine down on this kind of deal ever since 1991, when the Soviet Union disintegrated and left strategic nuclear weapons scattered across four new countries--Russia, Ukraine, Belarus and Kazakhstan.

In 1992, Kravchuk agreed in principle to give up Ukraine’s nuclear weapons. But his Parliament, fearful of Russia and suspicious that Ukraine was being bilked of the weapons’ value, dug in its heels.

By last summer, Ukraine’s economy was on its knees, and Kravchuk wanted a deal. Ukrainian and Russian negotiators worked out a swap of warheads for fuel, but they disagreed over the amount of compensation and the security guarantees that Ukraine wanted--and called on the United States for help.

U.S. officials, led by special envoy Strobe Talbott and Undersecretary of State Lynn Davis, went to work on the issue in September. But each time a deal looked close it fell apart--usually because Ukraine’s Parliament objected.

In October, Secretary of State Warren Christopher went all the way to Kiev just to get Kravchuk’s commitment to ratify the START treaty--but a few weeks later, Parliament added 13 conditions.

By December, however, Kravchuk wanted to try again. Ukraine’s economy was plummeting; its inability to pay for oil and gas from Russia forced households and offices to set their thermostats at 60 degrees. Moreover, the rise of Zhirinovsky raised the specter of a Russia that might use the nuclear issue as an excuse to dominate Ukraine once more.

Two U.S. ideas helped bring about the agreement, officials said. One was to strengthen the security assurances for Ukraine by having the United States and Russia reaffirm their commitment to secure borders under the 1975 Helsinki accord.

The other was to bring in a U.S. agency, the United States Enrichment Corp., to advance the money for an initial shipment of nuclear fuel rods to Ukraine.

Times special correspondent Mary Mycio in Kiev, and staff writers Richard Boudreaux in Moscow and Norman Kempster in Washington, contributed to this report.