New Start treaty: Obama signs US-Russia nuclear papers
US President Barack Obama has signed an arms treaty with Russia that would reduce the nations' nuclear arsenals and bolster verification mechanisms.
The Russian president signed similar documents last week, so the New Start treaty will come into effect when the papers are exchanged this weekend.
The treaty was approved by the US Senate in December and by the Russian parliament last month.
It replaces the 1991 Start treaty which expired in December 2009.
The New Start treaty, agreed to by Mr Obama and Russian President Dmitry Medvedev in April, limits each side to no more than 800 deployed nuclear warhead delivery systems (including bombers, missile launchers and nuclear submarines), a cut of about 50%. It limits each side to 1,550 deployed warheads.
It will also allow each side visually to inspect the other's nuclear capability, with the aim of verifying how many warheads each missile carries.
The White House barred reporters from the Oval Office when Mr Obama signed the treaty, but allowed still photographers.
The pact, opposed by many Republicans, could become an issue in the 2012 US political campaign.
Among other criticisms, US opponents of the treaty argued Russia would have reduced stockpiles anyway as its arsenal aged, so the US had no reason to agree to scrap its own nuclear arms.