Britain has welcomed the ratification of a US-Russian nuclear arms control treaty by the American Senate and urged Moscow to follow suit.
Foreign Secretary William Hague said the New Start treaty will "contribute to increased trust and security for all" and marked an important step towards the UK's long-term goal of a world without nuclear weapons.
Russia's parliament has not yet ratified the pact, signed by Barack Obama and Dmitry Medvedev in April, with politicians in Moscow arguing that they must analyse the Senate's conditions for its ratification before making their decision.
Mr Medvedev's spokeswoman said the Russian president welcomed Wednesday's ratification vote in Washington and hoped both houses of the Russian Parliament would do the same.
The treaty would limit each country to 1,550 strategic nuclear warheads, down from the current 2,200 cap. It would also establish a new monitoring and verification system.
In a statement released by the Foreign Office in London, Mr Hague said: "I welcome the ratification of the New Start treaty by the US Senate on December 22 2010.
"The United States and Russia together have 90% of the world's nuclear arsenals and this treaty will contribute to increased trust and security for all.
"It is also an important step towards our long-term goal of a world without nuclear weapons. We now look forward to ratification of the treaty by Russia and its subsequent entry into force."
He added: "The international community must now take advantage of this step to bring fresh momentum to implementation of all commitments under the Nuclear Non-Proliferation Treaty (NPT), specifically the action plans agreed at this year's successful NPT review conference.
"We look forward to working on this with the United States, Russia, and our other partners in the international community."