WASHINGTON — U.S. officials say that negotiations with Russia to replace an expired Cold War-era arms control treaty are unlikely to conclude by the end of the year as the White House had hoped.

As the two sides seek a breakthrough, U.S. President Barack Obama and Russian counterpart Dmitry Medvedev plan to discuss the nuclear negotiations in a meeting Friday on the sidelines of United Nations climate talks. But the two leaders are not expected to seal a deal.

U.S. officials, speaking on condition of anonymity because of the sensitivity of the talks, say that negotiations with Russia on a replacement for the Strategic Arms Reduction Treate have become hung up on a disagreement about how to monitor the development of new intercontinental ballistic missiles.

Russian President Dmitry Medvedev Photo by T

Alexander Nemenov