Washington (CNN) -- With the Senate set to begin its lame-duck session Monday, the Obama administration is telling members it's time for them to vote on the New START nuclear arms control treaty with Russia.
But midterm congressional elections have thrown a wrench into the administration's push for Senate ratification.
Some Republicans are slamming on the brakes, saying that, despite lengthy hearings in the last session, they still have more questions about the agreement. If there's no vote, new Senate hearings would be required and that could set back ratification for as many as two years.
The Democratic chairman of the Senate Foreign Relations Committee, John Kerry, said Wednesday he's "very hopeful" the Senate will vote in December. "We're going to try to move to the START treaty and we're going to get the START treaty done," he vowed.
Kerry said he has consulted with key Republican Sen. Richard Lugar, Secretary of State Hillary Clinton, Vice President Joe Biden and Republican Sen. Jon Kyl, who is leading the charge against voting on the treaty in the lame-duck session.
Kyl and other Republicans say they are not convinced the Obama administration is committed to modernizing the nations' nuclear arsenal or to developing and deploying a robust missile defense system.
Ellen Tauscher, under secretary of state for arms control and international security, told CNN, "We've had over 20 hearings and briefings, we have had over 900 questions for the record. ... All of these questions have been asked and answered."
"Some people on the other side are just not going to take yes for an answer, or no for an answer. But the president is working diligently to make it clear that the case has been made. And every day that we do not have the Senate ratify this treaty is one more day for mistrust and miscalculation that is unnecessary, because this is a treaty that will give us the kind of verifiability that we're looking for."
The treaty has been endorsed by the chairman of the Joint Chiefs of Staff, six former secretaries of state, five former defense secretaries and seven former Strategic Air Command chiefs.
Secretary of Defense Robert Gates has said, "Since the expiration of the old START Treaty in December 2009, the U.S. has had none of these [verification] safeguards," including no U.S. inspectors on the ground in Russia keeping an eye on Russia's weapons.
But opponents say there should be no rush to ratify. This week 11 former Republican senators wrote to Senate Majority Leader Harry Reid and Minority Leader Mitch McConnell, charging there are "serious concerns" about the treaty and urging them to put off the vote until the new Congress is in session next year.
"The complex national security issues raised by this treaty," their letter says, "questions of missile defense, tactical nuclear weapons, and verifiability, among others -- merit informed deliberation by the newly elected Senate, not a hastily deployed 'rubber stamp' from yesterday's Senate."
But Tauscher counters that two of those issues are not part of the START treaty: "This is a strategic arms control treaty. It doesn't deal with missile defense, where we have made very clear that no one is going to dissuade us from having the strongest missile defense that we believe we need. This is not about tactical nukes because it's about strategic nuclear weapons," she said.
"You can start to throw as many red herrings out of the pool as you want," Tauscher told CNN, "but the truth is that this is a follow-on treaty to an enormously successful one. It's a modest treaty, it's got modest reductions, but it does have 21st century technology in the inspections that give us more visibility and more transparency into what Russia's strategic forces are doing. And that is necessary for us to not get back into a world where mistrust and miscalculation cause us to make mistakes."
Arms control expert Sharon Squassoni, director and senior fellow of the Proliferation Prevention Program at the Center for Strategic and International Studies, told CNN the New START treaty, in many respects, "should have been a no-brainer."
"The reductions are modest," she said, "it reinstates verification measures lost under the Moscow Treaty, and its main objective was to reset relations with Russia. There is broad bipartisan support for it, so the only surprising fact is that it hasn't passed the Senate yet."
The START treaty, signed by President Barack Obama and Russian President Dmitry Medvedev in April, cuts each country's deployed nuclear warheads by approximately a third, limiting each side to a maximum of 1,550. Before it goes into effect it must be ratified both by the U.S. Senate and by the lower house of the Russian legislature, the Duma.
Reacting to the midterm election, in which Republicans made significant gains, the Duma's International Affairs Committee delayed consideration by the entire Duma. "They don't want to be caught in a situation similar to the one they were in with START II, which they ratified but the United States did not," Squassoni said.
If START is not ratified by the Senate, both supporters and critics told CNN, it could hurt president Obama's credibility not only with the Russians but internationally as well.
"If we don't get this ratified it's going to hamper our ability to move forward on a bigger agenda," Tauscher said. "If we don't ratify this, what do you think are our chances of beginning negotiations on tactical nukes? It is the start of a bigger agenda and, first things first, we need to get this ratified in order to move on to that other agenda."
Some observers say the debate over New START actually is not so much about the treaty itself as much as it is a way for Republicans to win concessions on their priorities, such as missile defense. One Russia expert from the conservative camp tells CNN that some Republicans also want to deny Obama a foreign policy victory.
Another expert, Samuel Charap of the Center for American Progress, who supports the treaty, told CNN he thinks the debate about New Start is "probably more of a negotiating tactic than a statement that 'we will not let it happen during the lame-duck session.'"
He says Obama, by including $80 billion over 10 years for nuclear weapons modernization in his budget, tried to pre-empt criticism that he is not doing enough on nuclear arms modernization.
"People who are ideologically opposed to arms control are playing the long game," Charap said, "attempting to make New START so expensive, both in terms of the budget and political capital, that more ambitious treaties will be 'out of the price range' of the executive branch in the future."
Kyl's spokesman, Ryan Patmintra, told CNN the senator "does not support the treaty or oppose it. He has reserved judgment on this treaty. ... He does not want to see a ratification process rushed."
Meanwhile, the two sides are talking. "They're pretty close," one arms control insider told CNN. "Now they're haggling over the price."