Senate debate on ratification of the new Strategic Arms Reduction Treaty could begin as early as Wednesday, although concerted Republican opposition to considering START remains a barrier to moving forward in the final days of the 111th Congress.

“It could be on the floor as early as tomorrow, but no final decision has been made,” Jim Manley, the chief spokesman for Senate Majority Leader Harry Reid (D-Nev.), said Tuesday morning.

Ratification of treaties requires 67 votes, and GOP support for START on its merits has been building.

But even those Republicans supportive of START — President Barack Obama’s top foreign policy priority — have threatened to withhold their vote absent sufficient time for debate and amendments. With final passage of the tax-cut extension and other legislative priorities still on the docket, it is not yet clear if enough floor time remains in the lame duck to also address START to the GOP’s satisfaction.

Reid had previously set Friday as the last day of session this year, although that could change. Senate Minority Whip Jon Kyl (R-Ariz.) signaled Monday that any attempt to clear START this week would result in the treaty’s failure to be ratified. Kyl also suggested Tuesday that nothing had changed in terms of his opposition to portions of START and related policy issues.

When asked Tuesday if he had an update to offer on the treaty’s progress vis-à-vis GOP support, Kyl said, “Not from me.” Asked further if he expected START to come up for consideration this week, Kyl added: “Not if they want to get it passed.”

A senior Republican Senate aide said Tuesday that nothing had changed. Meanwhile, negotiations between the White House, Senate Republicans and Senate Foreign Relations Chairman John Kerry (D-Mass.) continue behind the scenes in an effort to secure enough GOP votes to ratify START.