WASHINGTON – US President Barack Obama warned members of the US Senate Saturday that their failure to ratify a new nuclear arms reduction treaty with Russia before the end of the year could set back relations with the former Cold War rival.

"Without a new treaty, we'll risk turning back the progress we've made in our relationship with Russia, which is essential to enforce strong sanctions against Iran, secure vulnerable nuclear materials from terrorists, and resupply our troops in Afghanistan," Obama said in his weekly radio address.

"And we'll risk undermining American leadership not only on nuclear proliferation, but a host of other challenges around the world," he added.

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.

Republicans have said they need to be sure that the US nuclear arsenal will be modernized and that the treaty will not hamper US missile defense efforts -- but some acknowledged privately that they did not want to hand Obama a major diplomatic victory before the elections.

The task of ratifying the accord will be even tougher in January when a new Congress, elected in November 2 polls in which Republicans routed Democrats, takes office.

However, Obama argued that the START treaty "will reduce the world's nuclear arsenals and make America more secure."

He also cited remarks by General Hoss Cartwright, the vice-chairman of the Joint Chiefs of Staff, who said this past week that the military needed this accord.

"Ratifying a treaty like START isn't about winning a victory for an administration or a political party," the president noted. "It's about the safety and security of the United States of America."

However, the arms treaty risks becoming hostage of other hot-button issues facing Congress at the end of the year.

Obama's Republican foes in the Senate warned him Friday to drop plans to repeal a military ban on gays serving openly or risk the fate of the START Treaty.

Republican lawmakers who had previously indicated support for the accord expressed anger at key procedural votes Saturday on the "Don't Ask Don't Tell" prohibition and an immigration measure.

Democratic Senate Majority Leader Harry Reid's decision to push ahead with both proposals, which are fiercely opposed by Republicans, came with the White House on a quest for Republican support necessary to ratify the treaty.

Republican Senator Bob Corker, who has played a key role in debates on the accord, one of Obama's top foreign policy priorities, said Reid's move "poisons the well on this debate on something that's very, very important."

"I'm hoping that those will be taken down or I don't think the future of the START treaty over the next several days is going to be successful, based on what I'm watching," in meetings with fellow Republicans, he warned.

In response, Democratic Senator John Kerry, chairman of the Senate Foreign Relations Committee, said "my hope is that everybody will simply rise above whatever, however they want to view these votes."

Number-two Senate Republican Jon Kyl, his party's point man on the treaty, seemed to echo Corker when asked whether there was any connection between the treaty and the repeal vote.

"The only linkage is that the problem of having all of these political votes is that it certainly doesn't help create an atmosphere of cooperation on other issues," he said.

The DREAM Act, aimed at helping children of undocumented immigrants stay in the United States, was expected to fail its procedural test, but Democrats were thought to have the 60 votes to move forward with the repeal.

This video is from the White House, broadcast Dec. 18, 2010.