WASHINGTON, April 12 - Ukraine announced Monday that it has agreed to give up its highly enriched uranium, at the start of a nuclear nonproliferation summit called by U.S. President Barack Obama.

The announcement, made by White House press secretary Robert Gibbs, came after Obama's meeting with President Viktor Yanukovych. It was their first face-to-face meeting since Yanukovych's February inauguration.

Gibbs said the U.S. has been working to secure Ukraine's highly enriched uranium for a decade, calling Monday's announcement "just the kind of step we want to see at this summit."

Ukraine agreed to give up its roughly 90-kilogram stock of highly enriched uranium by the next Nuclear Security Summit scheduled to be held in the summer of 2012, much of it this year.

The amount is sufficient to make "several nuclear weapons."

Ukraine will convert its research reactors from highly enriched to low-enriched uranium, as Obama has been seeking to focus on protecting the world's stockpiles of nuclear materials from terrorist organizations pursuing the bomb.

“Viktor Yanukovych emerged Monday as an unlikely star among the four dozen foreign leaders President Obama gathered in Washington for his security summit,” Jackson Diehl of The Washington Post wrote.

The announcement “gave Obama one of the most tangible results of the summit,” Diehl wrote. “It also signaled Yanukovych’s ambition to position Ukraine between Russia and the NATO powers -- outside the Western alliance, but also not part of a Russian sphere of influence.”

Yanukovych outlined that strategy in an interview Monday afternoon with The Washington Post.

“The policy of the new administration of Ukraine is to strike the right balance in our relations with Russia and the European Union,” Yanukovych said. “We want to be a reliable bridge between Europe and Russia.”

This means, in part, an end to the previous government’s policy of seeking full membership in NATO -- a cause that the alliance endorsed in principle at the urging of the Bush administration, but then put on a back burner.

“The relations between Ukraine and NATO are not going to change,” Yanukovych said. “They will stay on the same level and with the previous attention. The only thing that has changed is that Ukraine as a non-bloc member is not stating that it wants to accede to NATO” -- because the majority of Ukrainians oppose full membership. “We will keep developing partnership interests,” he added. “We will keep improving that.”

At the same time Yanukovych made clear that he did not intend to go along with Moscow’s wish that his government join a customs union with Russia, Belarus and Kazakhstan, instead of seeking a free trade agreement with the European Union.

“At this stage the accession of Ukraine to the customs union isn’t possible,” he said -- but he hopes to finish a trade agreement with the European Union by the end of the year.” (wp/ez)