A summit on nuclear security, to involve Russia and the U.S., has been postponed until May 2010, a top U.S. State Department official said on Wednesday.

Speaking at the George Washington University, Under Secretary of State for Arms Control and International Security Ellen Tauscher said the summit was delayed due to Easter holidays.

The event was initially scheduled for April.

President Dmitry Medvedev said at a news conference following the G20 summit in Pittsburgh that Russia and the U.S. have agreed to jointly prepare for the summit on the nuclear security to be held in Washington, D.C., in 2010.