Washington (CNN) -- A key Republican senator cast doubt Tuesday on the Obama administration's chances of passing the nuclear treaty with Russia during the lame-duck session of Congress.
Sen. Jon Kyl, R-Arizona, who is taking the lead for Republicans on negotiating with the administration on ratification of the New Strategic Arms Reduction Treaty (New START), said in a statement he told Senate Majority Leader Harry Reid, D-Nevada, that the accord should not be considered before January, when the newly elected Congress is seated.
"When Majority Leader Harry Reid asked me if I thought the treaty could be considered in the lame-duck session, I replied I did not think so given the combination of other work Congress must do and the complex and unresolved issues related to START and modernization," Kyl said.
"I appreciate the recent effort by the Administration to address some of the issues that we have raised and I look forward to continuing to work with Senator [John] Kerry, DOD, and DOE officials," he said, referring to the Massachusetts Democrat and the departments of defense and energy.
Alarmed Democrats were quick to respond, arguing that it would be dangerous to delay consideration of the treaty.
Vice President Joe Biden released a statement warning that "failure to pass the [new treaty] this year would endanger our national security. Without ratification of this treaty, we will have no Americans on the ground to inspect Russia's nuclear activities, no verification regime to track Russia's strategic nuclear arsenal, less cooperation between the two nations that account for 90 percent of the world's nuclear weapons, and no verified nuclear reductions."
Biden called the treaty "a fundamental part of our relationship with Russia, which has been critical to our ability to supply our troops in Afghanistan and to impose and enforce strong sanctions on the Iranian government."
The vice president said the administration will continue to seek Senate approval of the treaty before the end of the year.
Kerry said he had talked with Kyl and does "not believe the door is closed to considering [the treaty] during the lame duck session."
"Ratifying New START is not a political choice, it's a national security imperative," he declared.
The White House said it has been working to allay Kyl's concern, even sending three administration officials to meet with him last week and offering an additional $4.1 billion for modernization of the weapons program. Still, despite the outreach, the White House only learned of Kyl's opposition to taking up the vote during the lame-duck session "via the press," a senior administration official said. Hours later the White House issued the strongly worded statement from the vice president.
"The key point is that Senator Kyl has always asked for more funding to modernize the nuclear stockpile. An offer to do exactly that was made to Kyl in a three-hour briefing on Friday, in person," the official said. "Additionally, there has been an extraordinary amount of consultation with the Senate."
State Department spokesman P.J. Crowley also weighed in, saying that "we believe that we've answered all of their questions. We've addressed ... concerns that Sen. Kyl and others have expressed about ensuring that there is an effective modernization program as a companion to the New START treaty."
Crowley promised that the administration will continue to engage Kyl and others "in good faith."
The White House is offering to spend $4 billion more over five years for nuclear weapons modernization, in an effort to win over Kyl and other holdout Republicans who have questioned whether the Obama administration will provide enough money for modernization of the nuclear force remaining after the proposed START cuts the number of deployed warheads to 1,550.
CNN's Alan Silverleib and Laurie Ure contributed to this report