US President Barack Obama and Russian President Dmitry Medvedev have inked a preliminary nuclear deal at a Moscow summit.

U.S. President Barack Obama and Russian President Dmitry Medvedev sign agreements in Moscow, capital of Russia, July 6, 2009. Obama and Medvedev signed a joint statement on anti-missile issue and a new arms reduction agreement here on Monday. [Lu Jinbo/Xinhua]

The two sides agreed to reduce the world's two largest nuclear stockpiles by as much as a third, down to the lowest levels of any US-Russia accord.

The document signed by the two leaders is meant as a guide for negotiators. It will be used as the nations' work toward a replacement pact for the Strategic Arms Reduction Treaty that expires in December.

The joint understanding also commits the countries to lower longer-range missiles for delivering nuclear bombs to between 500 and 11-hundred.

The limit for warheads would be in a range of 15-hundred to 1,675 each.

A White House statement said the new treaty "will include effective verification measures." And Obama claims the deal will be completed by the end of the year.

Barack Obama, US President, said, "We've taken important steps forward to increase nuclear security and to stop the spread of nuclear weapons. This starts with the reduction of our own nuclear arsenals. As the world's two leading nuclear powers, the United States and Russia must lead by example, and that's what we are doing here today."