Russia's parliament has given its backing to the Start nuclear arms disarmament treaty. The Federation Council (upper house) unanimously approved the deal signed by US President Barack Obama and Russia's Dmitry Medvedev in April 2010.
Under the agreement, the number of nuclear warheads deployed by each country will be cut to 1,550.
The US Senate approved the treaty by 71 votes to 26 last year, after months of wrangling.
Wednesday's vote by the Federation Council comes a day after the treaty was ratified by the Duma, or lower house, and represents the final step in its passage through parliament.
The New Start (Strategic Arms Reduction Treaty), will replace its predecessor, signed in 1991, which lapsed at the end of 2009.
The treaty will bring about a cut in warheads of about 30% from the previous limit and will also allow each side visually to inspect the other's nuclear capability, with the aim of verifying how many warheads each missile carries.
In addition, there will be legally binding limits on the number of warheads and missiles that can be deployed on land, on submarines, and on bombers, at any one time.
