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Crowley said the U.S. delegation, led by Assistant Secretary Rose Gottemoeller, has returned from Geneva for a recess.
"Our goal remains to conclude a solid treaty for the president's signature as soon as possible, and we expect that the teams will resume their negotiations in Geneva in mid-January," Crowley said in a regular state department briefing.
The U.S. and Russian teams have been in intense talks in the past few months to clinch an agreement over the successor treaty to the START, which expired on Dec. 5. The eighth round of talks was held in Geneva on Nov. 9 - Dec. 19.
U.S. President Barack Obama said the sides are "quite close to an agreement" on further nuclear arms reduction after his latest meeting with his Russian counterpart Dmitry Medvedev on the sidelines of the UN climate talks in Copenhagen last week.
The Russian president said some technical details require "further work."
Crowley said the talks involve "complex issues" in terms of "numbers, verification and kinds of systems," but he expressed confidence that the two sides will arrive at a satisfactory conclusion and agree on a new treaty that meets the national interests of both the United States and Russia.
Steven Pifer, an expert in arms control in think tank Brookings Institution, said in an interview with Xinhua that he thinks the remaining issue between the two sides are probably verification details.
He said the Russians probably want to reduce the amount of telemetry they share, which is the data that a missile broadcast during test shots.
"With telemetry access, we'll have a good understanding of Russian missile performance, they'll have a good understanding of American missile performance, that kind of transparency is very reassuring," Pifer said.
The START, signed in 1991 between the United States and the Soviet Union, obliged both sides to reduce the number of their nuclear warheads to 6,000 and delivery vehicles to 1,600.
The new treaty's outline agreed by Obama and Medvedev at a July summit in Moscow included slashing nuclear arsenals to 1,500 to 1,675 operational warheads and delivery vehicles to 500 to 1,000.