WASHINGTON (AFP) - US President Barack Obama on Wednesday extended for another year a freeze on Iranian assets in the United States first imposed 31 years ago by president Jimmy Carter. In a notice published by the White House, Obama noted that ties between the two countries had yet to be normalised, giving grounds for a continuation of a national emergency with respect to Iran. Carter had ordered a freeze on Iranian government assets under US jurisdiction on November 14, 1979, 10 days after militants and students sympathetic with the Islamic revolution overtook the US embassy in Tehran. Iranian militants held 52 US diplomats hostage for 444 days, and Washington and Tehran broke ties in April 1980. Obama extended the asset freeze just as the United States and other world powers are seeking to break the deadlock over Irans nuclear programme. A European diplomatic source said Tuesday that Iran has proposed a resuming long-stalled nuclear negotiations with major world powers in Istanbul on November 23 or December 5. EU chief diplomat Catherine Ashton had earlier proposed talks in Vienna from November 15 to November 18. Nuclear talks between Iran and the so-called P5+1 - Britain, China, France, Russia, Germany and the United States - have been deadlocked since October 2009 when the two sides met in Geneva.