US President Barack Obama will formally sign ratification papers for a new Russia-US disarmament treaty today, which slashes existing warhead ceilings by 30 percent over the next 10 years. Officials said Obama will make the ceremonial gesture in the Oval Office, before the milestone pact comes into force on February 5 at a ceremony in Munich attended by the two nations' top diplomats. Russian President Dmitry Medvedev signed the new START agreement's ratification on Friday after the Russian parliament passed the pact, which was endorsed by the US Senate last month. The new START sets the lower warhead ceiling and limits each side to 700 deployed long-range missiles and heavy bombers, and forms one of the most significant foreign policy successes of Obama's presidency so far.