Ukrainian President Viktor Yanukovich agreed on Monday to give up all the stockpile of highly enriched uranium in Ukraine by 2012, said the White House.

White House spokesman Robert Gibbs made the announcement minutes after U.S. President Barack Obama met with Yanukovich on the margins of the Nuclear Security Summit, which is being held in Washington.

"This is something the United States has tried to make happen for several years," said Gibbs, adding that Ukraine is expected to eliminate all the materials by the next nuclear security summit in 2012.

He called Ukraine's decision a "positive step" for preventing nuclear materials from being obtained by terrorists.

Gibbs said the United States will provide "some degree of both technical and financial assistance to ensure that it happens."

During the two-day summit hosted by President Obama, leaders from 47 nations will discuss ways of securing nuclear materials from terrorists -- "the most immediate and extreme threat to global security" as identified by Obama.

The summit will focus on the security of nuclear materials, leaving other broad topics such as non-proliferation, disarmament and peaceful nuclear energy to different forums, said the White House in a statement.

The presidents' meeting was the first since Yanukovich was elected Ukrainian president in February.

The United States officially recognized the independence of Ukraine in December 1991 following the dissolution of the Soviet Union. The Orange Revolution in Ukraine has led to closer relations between Kiev and Washington.

As a uranium-rich country, Ukraine has plentiful amounts of highly enriched uranium, which could be used as key materials for producing nuclear weapons. The United States has wanted to buy the materials from Ukraine.

By signing the Charter on Strategic Partnership with Ukraine in December 2008, the United States vows to support Ukraine's sovereignty and territorial integrity, as well as its "Euro- Atlantic aspirations and integration into the institutions of the Euro-Atlantic."

Russia has expressed strong objections to the U.S.-backed efforts to let Ukraine join the NATO military alliance.

Early in March, Yanukovich made his first visit as the president to Moscow and promised a "sharp turn" in the Ukraine- Russia relations.