President Barack Obama urged the full US Senate Thursday to approve a landmark nuclear treaty with Russia, after the pact won a key committee's crucial support despite stiff Republican opposition.

"I urge the full Senate to move forward quickly with a vote to approve this Treaty," Obama said after the Senate Foreign Relations Committee endorsed the new Strategic Arms Reduction Treaty (START) by a 14-4 margin.

The panel's action sent the agreement to the full Senate for a final vote expected this year, but after the November 2 mid-term elections, with the outcome uncertain because of Republican resistance.

"Ratification of this treaty will reinforce our cooperation with Russia on a range of issues, including one of our highest priorities -- preventing the spread of nuclear weapons," said the president.

The treaty -- signed by Russian President Dmitry Medvedev and Obama at an elaborate ceremony in Prague in April -- restricts each nation to a maximum of 1,550 deployed warheads, a cut of about 30 percent from a limit set in 2002.

The agreement, a top Obama foreign policy initiative, replaces a previous accord that lapsed in December 2009 and also requires ratification by Russia's lower house, the Duma.

"I personally believe we will have the votes to ratify this," Democratic Senator John Kerry, the committee's chairman, said after the panel acted. "The stakes are enormous."

US Senate ratification requires 67 votes, Democrats control 59 seats, and just three Republicans on Kerry's committee voted in favor of the accord, with four against.

"When we ratify this treaty, we limit Russia's nuclear arsenal, regain the ability to inspect their nuclear forces, and redouble international support for our nonproliferation efforts to counter the spread of nuclear weapons to rogue nations like Iran and North Korea," said Kerry.

Republicans have charged the accord could hamper US missile defense plans -- a charge denied by the Pentagon -- have concerns about Russian implementation, and want assurances about plans to modernize the existing US nuclear arsenal.

The panel approved by voice vote a resolution of ratification authored by its top Republican, Senator Richard Lugar, to address those concerns, with Republican Senator James Risch the sole "no."

Lugar said his resolution declared that the treaty "imposes no limitations on the development and the deployment of US missile defenses" apart from forbidding the conversion of some existing launch mechanisms.

It also restated US policy to deploy a missile defense system to thwart rogue launches as soon as technologically possible, and emphasized the importance of ensuring Russian compliance and modernizing the US arsenal.

Lugar also highlighted that US inspectors in Russia had been unable to do their jobs since the previous treaty lapsed, and stressed the need to have US "boots on the ground" to verify compliance.

Risch said the US intelligence community had provided "troubling" information recently to the Senate Intelligence Committee, but Kerry shot back that the community had also not changed its support of the treaty.

Lawmakers were tight-lipped about the details, but the top Republican on the Senate Intelligence Committee, Kit Bond, warned in a statement about "the treaty's lack of verification necessary to detect Russian cheating."

Asked whether there was anything new given longstanding allegations of Russian non-compliance, Risch told reporters: "You haven't seen the same stuff I've seen," but would not elaborate.

Risch won committee approval of an amendment calling for modernizing the US nuclear arsenal, even as the panel rejected several amendments that Kerry warned would have the effect of killing the treaty.

The panel also approved, after diluting it, an amendment from Republican Senator Jim DeMint recommitting Washington to deploying a missile defense system -- a proposal that has drawn frequent, angry opposition from Moscow.

DeMint was absent for the vote.