American President Barack Obama will repeat today the request to reduce the stockpile of nuclear weapons in the world.
Obama will present his position during today's address at the Brandenburg Gate in Berlin.
The official, who asked to remain anonymous, said Obama would again ask Congress to ratify the nuclear test-ban treaty.
A senior US government official said Obama would propose cutting the US and Russian stockpiles by one-third, bringing the number of warheads in both countries to around 1.000.
Obama is not expected to propose a timetable for achieving that goal. He discussed the end of stockpile expansion with Russian President Vladimir Putin during the G8 summit in Northern Ireland.
During his first term, the US and Russia agreed to reduce their stockpiles of nuclear weapons to around 1.550 warheads.
The official, who asked to remain anonymous, said Obama will again ask Congress to ratify the nuclear test ban treaty.
It is not clear whether he will seek further cuts through the new deal or try to reach a non-binding agreement that does not have to be approved by Congress.
The size of the stockpile of nuclear weapons is a closely guarded secret in most countries that possess them, but nuclear policy experts say that, apart from the US and Russia, no country has more than 300.
According to the Federation of American Scientists, France has about 300, China about 240, Britain about 225, while Israel, India and Pakistan have about 100 nuclear bombs each.
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