A senior senator offered a plan Monday aimed at overcoming objections by his fellow Republicans to a nuclear arms control treaty with Russia.

The proposal by Indiana Sen. Richard Lugar came as Obama administration officials made a last-minute push for the New START agreement ahead of a vote Thursday in the Senate Foreign Relations Committee. While the panel is expected to endorse the treaty, prospects are uncertain in the full Senate, where Democrats need at least eight Republican votes for ratification.

Administration officials were expressing confidence that the treaty, considered one of President Barack Obama's top foreign policy achievements, was gaining support from Republicans despite the rarefied political environment ahead of the November congressional election.

"There is a great deal of momentum toward ratification," said the treaty's chief U.S. negotiator, Rose Gottemoeller, at an event at Georgetown University on Monday.

Delays in negotiating the treaty and moving toward ratification have pushed consideration into the political season ahead of November's elections, when Republicans are reluctant to allow a policy victory for the Obama administration.

Obama and Russian President Dmitry Medvedev signed the treaty in April. It would shrink the limit on strategic warheads to 1,550 for each country, down about a third from the current ceiling of 2,200. It also would implement changes in current procedures that allow both countries to inspect each other's arsenals and verify compliance.

Lugar, the Foreign Relations Committee's ranking Republican and a longtime advocate of arms control, was circulating an amendment to the resolution of support for the treaty offered by the committee's chairman, Democrat John Kerry of Massachusetts.

The amendment, obtained by The Associated Press, includes assurances about a host of concerns that Republicans have raised about the treaty, including whether it would limit U.S. missile defense. The amendment says it is the sense of the U.S. Senate that the treaty does not limit U.S. missile defense except for a provision that forbids converting existing offensive missile launchers into missile defense assets.

The resolution also says that a unilateral statement by Russia after the treaty was signed in April, in which Moscow made clear that it could withdraw from the treaty if it should feel threatened by a U.S. missile defense systems, "does not impose a legal obligation on the United States."

Because some Republicans have said that before ratifying the treaty they want to be sure that the Democrats will pass a big boost in money for maintaining and modernizing the U.S. nuclear stockpile, the Lugar amendment also includes provisions that would require the White House to consult with the Senate on funding levels to ensure adequate funding.