US Secretary of State Hillary Clinton said Thursday she hoped the "lame-duck" session of Congress would pass a new nuclear disarmament treaty with Russia, but she could not guarantee it.

Sweeping Republican gains in Congress mostly will not become a reality in Washington until winners from Tuesday's vote are sworn in come January, giving Democrats a narrow "lame-duck" session to wrap up unfinished business.

That includes passing the new Strategic Arms Reduction Treaty (START), which US President Barack Obama and his Russian counterpart Dmitry Medvedev signed in April.

"We believe we have enough votes to pass it in the Senate. It's just a question of when it will be brought to the vote," Clinton told reporters during a visit to Wellington, New Zealand, during a tour of Asia.

Sixty-seven votes are required for ratification in the 100-member Senate.

"It certainly would be my preference that it be brought in any lame-duck session in the next several weeks and that is what I am working toward seeing happen," the chief US diplomat said.

"But we will have to wait and work with the Senate and the leadership when they come back for that session," Clinton added.

"Both the United States and Russia are committed to ratifying it," she said.

In Moscow, following the US elections, the Russian parliament's foreign affairs committee withdrew its recommendation to ratify the treaty in the Duma, or parliament, an official said Wednesday.

"If the 'lame duck' senators from the old make-up cannot do this in the next weeks then the chances of ratification in the new Senate will be radically lower than they were until now," said the chairman of the Duma's foreign affairs committee Konstantin Kosachev.

Republicans failed to capture the Senate but cut deeply into the Democratic majority by picking up at least six seats in the upper chamber after bitterly fought mid-term elections.

Republicans were set to control 42 of 100 Senate seats, up from 41, in the lame-duck session after Representative Mark Kirk won a special election for Obama's old spot.

The START treaty restricts each nation to a maximum of 1,550 deployed warheads, a cut of about 30 percent from a limit set in 2002.