WASHINGTON - President Obama on Thursday forcefully rejected Republican accusations that his foreign policy was timid and amounted to a policy of "appeasement."

"Ask Osama bin Laden and the 22 out of 30 top al-Qaeda leaders who have been taken off the field whether I engage in appeasement. Or whoever is left out there, ask them about that," the president said during a news conference.

He also defended his efforts to block Iran from building a nuclear weapon, saying Tehran was now isolated and facing tough international sanctions thanks to the work of his national security team.

His remarks came a day after Republican presidential candidates took turns criticizing Obama's foreign policy as weak during speeches before Jewish activists and donors. They especially focused on the Obama administration's Middle East policy.

Former Sen. Rick Santorum of Pennsylvania on Wednesday said Obama's policy toward radical Islamists "has been nothing but appeasement."

Obama seemed primed for the question about the critique, and his communications director, Dan Pfeiffer, promptly posted the president's response on Twitter: "Ask Osama Bin Laden."

Former Massachusetts Gov. Mitt Romney on Wednesday said Obama "emboldened Palestinian hard-liners who now are poised to form a unity government with terrorist Hamas and feel they can bypass Israel at the bargaining table."

Romney also accused Obama of being "timid and weak in the face of the existential threat of a nuclear Iran."

Obama, citing "some of the political noise out there," said his administration had "systematically imposed the toughest sanctions" on Iran.