The announcement by Ukrainian President Viktor Yanukovich followed his meeting with President Obama before the start of a 47-nation summit on nuclear security.

"The Ukraine has quite a number of power plants and various universities and research institutes where we are trying to understand to best utilize nuclear in a peaceful means,"

A White House statement said Obama "praised Ukraine's decision as a historic step and a reaffirmation of Ukraine's leadership in nuclear security and nonproliferation."

The White House statement said the United States will provide financial and technical assistance to Ukraine to get rid of its highly enriched uranium.

According to Gibbs, the uranium that Ukraine will give up is enough to construct several nuclear weapons. He said Ukraine would convert its nuclear energy facilities to operate on low-enriched fuel.

The United States was prepared to help other nations take similar steps to Ukraine's, Gibbs said.

"The goal is to do all that we can," Gibbs said, adding: "Our assistance and the assistance of our partners and our allies will be important, not just this week but in the coming years."