KIEV, Ukraine (AP) _ Ukraine and the Group of Seven nations failed to agree Thursday on how to pay for completion of two nuclear reactors to compensate for closing the Chernobyl nuclear plant.

The top Ukrainian top negotiator warned that without the funding, Ukraine would put off shutting the plant until sometime after the previously promised deadline of 2000.

Negotiators for the leading industrialized nations known as the G-7 took a brighter view.

``This should not prompt doubt in Ukraine that the G-7 nations will not fulfill their political promises,'' said Claude Mandil, the top energy official at France's Industry Ministry and head of the G-7 team. He said the money would probably be released in mid-1997.

The pledge was made last December, when the G-7 nations said they would give $3.1 billion in aid to help Kiev close Chernobyl, site of the world's worst nuclear disaster.

On April 26, 1986, Chernobyl's reactor No. 4 exploded during a test of its turbines, spewing a cloud of radiation across Europe.

Ukrainian President Leonid Kuchma has promised to close Chernobyl's reactor No. 1 this fall. It is one of two reactors at the plant still functioning.

But Ukraine's parliament has resisted the closure, saying the country needs the electricity and jobs Chernobyl provides. It is considering ways to override Kuchma's promise and keep the reactors running.

Some of the G-7 money will go to Ukraine's failing energy sector _ including the completion of two reactors at other Ukrainian nuclear plants.

At the G-7 nuclear summit in Moscow in April, Western leaders promised the money for the reactors by the end of this year.

But in negotiations in Kiev on Thursday, the two sides did not work out a financing plan for the reactors, which Ukraine fears will delay the process.

``If there is no decision acceptable for Ukraine's economy, the Ukrainian government will be forced to review the deadline for fulfilling the Chernobyl program,'' Yuri Kostenko, Ukraine's top nuclear safety official, told a news conference.

The next round of talks with the G-7 is tentatively scheduled for September.