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 Nov. 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. – Agence France