The United States and Russia say, they were on the verge of clinching a sweeping new nuclear disarmament pact, but signalled the bid to smooth final technical issues would slip into January. US President Barack Obama and Russian President Dmitry Medvedev held their latest summit on the sidelines of the UN climate talks in Denmark, but dashed speculation that the long-awaited deal would be signed by the end of the year. Obama said the two sides were "quite close" to clinching a framework to decommission hundreds of nuclear arms, and replace the 1991 Strategic Arms Reduction Treaty (START) which expired on December 5. The United States has said it currently has some 2,200 nuclear warheads, while Russia is believed to have about 3,000. The new treaty is the centerpiece of Obama's attempt to "reset" previously strained ties between Moscow and Washington, and would yield important symbolic weight in his top priority effort to quell nuclear proliferation.