US President Barack Obama sharply criticized the Iranian regime's repression of opposition protesters Monday in some of his toughest comments on behalf of those challenging the Iranian government."The United States joins with the international community in strongly condemning the violent and unjust suppression of innocent Iranian citizens," Obama said, taking a break from his vacation in Hawaii to speak about the violence in Iran and the attempted terror attack on a Detroit-bound plane on Christmas Day.He referred to the "iron fist of brutality" which has greeted the protesters, even on "solemn occasions and holy days" such as this weekend over the sober holiday of Ashura, during which government forces killed at least eight demonstrators."The United States stands with those who seek their universal rights," Obama declared, calling for the government to respect its citizens' rights and release those "unjustly detained" there."We will continue to bear witness to the extraordinary events that are taking place there," he concluded. "And I'm confident that history will be on the side of those who seek justice."Patrick Clawson of the Washington Institute for Near East Policy said the change towards strong public support for the opposition contrasts greatly with the "much less vigorous" statements Obama made when the protests first broke out after June's flawed presidential election took place.At that time, Obama intimated that the main US priority remained the nuclear program - over which it was undertaking negotiations with the regime - and that too vocal American support for those challenging the government could undermine the reformists as illegitimate agents of the West."Neither of those two undertones were present in the statements that the president made Monday. That's a change. I don't want to say it's an 180-degree change, but it's a change," Clawson said. "It reflects an appreciation on the part of the administration that this opposition movement isn't going away."Former State Department official Suzanne Maloney said that while a more cautious stance was warranted in the immediate aftermath of the elections, when it wasn't clear how long-lived or robust the protests would be, those concerns were now no longer relevant."There's no prospect that an American embraceâ€¦ is going to taint what is a very sustained, authentic Iranian movement," she said.The more muscular US rhetoric also comes at a time when the administration had promised a review of its Iran policy and suggested that a shift towards sanctions would be coming in response to Teheran's recalcitrance in negotiations over its nuclear program."This was, of course, the time frame for the overall policy shift," noted Maloney, who is now a senior fellow at the Brookings Institution's Saban Center for Middle East Policy. "It's a convenient time for the president to rediscover the importance of speaking out on human rights issues."Clawson, though, stressed that the driving force of US policy continues to be the nuclear program. He pointed to Iran's backtracking on the offer to ship much of its enriched uranium abroad for conversion for medical use worked out by international negotiators this fall."The real shift came in the rejection of the research reactor deal, and this just reinforces their attitude."Putting US support of the opposition movement in that context could lead to different interpretations on the president's motives and meaning.Clawson suggested it would be possible for the US to use Obama's outspokenness to chastise the regime for not being more forthcoming on the nuclear front.The White House did not immediately respond to a request for clarification on its policy.