In a speech marking the opening a new Middle East think tank Thursday, Secretary of State Hillary Rodham Clinton called Thursday on Israeli Prime Minister Benjamin Netanyahu to prove his commitment to a Palestinian state, warning that prolonged conflict only strengthened extremists.

Speaking at a dinner attended by the ambassadors of Israel and several Arab states, Clinton was forthright in her demands of Netanyahu, urging Israel to "refrain from unilateral statements and actions" that could undermine peace.

"Prime Minister Netanyahu has embraced the vision of the two-state solution," Clinton said.

"But easing up on access and movement in the West Bank, in response to credible Palestinian security performance, is not sufficient to prove to the Palestinians that this embrace is sincere," she said.

"We encourage Israel to continue building momentum toward a comprehensive peace by demonstrating respect for the legitimate aspirations of the Palestinians, stopping settlement activity and addressing the humanitarian needs in Gaza."

On a visit to Israel last month, Vice President Joe Biden was said to have argued that Middle East peace would help improve the safety of the tens of thousands of US troops stationed in Afghanistan and Iraq.

Biden's trip turned into a fiasco when Israeli officials announced plans to build 1,600 Jewish settlements in annexed East Jerusalem while he was still on the visit. Clinton later called the Israeli move "insulting."

The Obama administration has come under harsh attack by some of Israel's supporters in Washington, who say that the United States is putting the Jewish state at risk. Representative Eric Cantor, the number two Republican in the House, said the White House "has applied a severe double standard that refuses to hold the Palestinians accountable for their many provocations."

"It makes one wonder — where the responsible adults are in the administration?" said Cantor, the only Jewish House member from the minority party.