President Obama will not achieve a breakthrough on nuclear arms reductions when he meets with Russian President Dmitri Medvedev, US officials said Sunday.

"There is a long way to go before finishing a treaty," said Gary Samore, senior director for arms control with the National Security Council. "There is no agreement on the end deal."

The US and Russia are racing against a December 5 deadline to formulate a new arms control protocol to replace START (Strategic Arms Reduction Treaty), which expires on that day.

Obama and Medvedev will announce Monday that they have achieved "some progress" to mutually reduce the number of nuclear delivery systems below 1,600 and nuclear warheads below 2,200. Those are the numbers codified in START, signed in 1991 and ratified in 2001. The treaty reduced about 80 percent of the strategic nuclear arms possessed by both countries.

The 700-page treaty covers every aspect of nuclear arms control. It's sprinkled with dense language on inspection and verification of nuclear arms, delivery systems and angels-on-the-head-of-a-pin specificity about what constitutes a moth-balled delivery system or warhead.

The language reflects deep mistrust of the former Cold War enemies. Even though neither nation considers the other a foe, arms control language is difficult to dismantle entirely and differences over definitions remain.

For example, the US no longer uses B-1 and B-52 bombers to carry nuclear warheads and some of the B-52s are no longer air-worthy. For this reason, Samore says they shouldn't be counted in the new START's delivery system matrix. The Russians want them counted because they could still deliver nuclear bombs if the US decided to re-arm and re-tool them for nuclear-armed flight.

There are other sticky issues outside the treaty, too. Russia wants to link a deal with the US on the future of ballistic missile defense systems in Europe with the new START framework. The US opposes such linkage, arguing the US system poses no threat to Russia's nuclear weapons or its sovereignty.

"It's modest," Samore said of the proposed US ballistic missile defense system that would seek to shield Europe from attacks from North Korea and, if it developed nuclear weapons and missiles, Iran.

The missile defense system, a program started under the Bush administration in 2002, raised issues from the beginning with Russia, which argued it would lead to a new arms race. In 2007, President Bush and then Russian President Putin argued over a new plan by the United States to position interceptor missiles and radar interceptors in Poland and the Czech Republic.

Overall, the White House is pleased with how negotiations between the two nations has progressed since April, when the two leaders met for the first time in London at the G20 summit, but downplayed expectations that the White House was hoping for any large scale announcements for this trip to Moscow. "These things take years to negotiate," Samare said. "We're really trying to do this in double quick time."