WASHINGTON - President Obama reassured a powerful pro-Israel group that America's support for the Jewish state's security is "ironclad," but he insisted on a sense of urgency about reviving peace talks that he said would require both Israelis and Palestinians to make "hard choices."

"The current situation in the Middle East does not allow for procrastination," Obama said, adding that he had expressed that impatience to Israeli Prime Minister Benjamin Netanyahu in their private meeting Friday.

The comment was one of several that seemed designed to push Israel's current leaders outside their comfort zone, even at the risk of creating tension in the U.S.-Israeli relationship. Taken together with Obama's long address on Middle Eastern policy Thursday, the remarks to the American-Israel Public Affairs Committee appeared to show a renewed confidence on the president's part about his ability to push an ambitious Middle East agenda.

"There is an impatience with the peace process, or the absence of one, not just in the Arab world - in Latin America, in Asia, and in Europe," Obama said. "That impatience is growing, and it's already manifesting itself in capitals around the world."

Netanyahu had publicly lectured Obama after their meeting. He objected to the president's formula, set out in a speech Thursday, that negotiations should have as their starting point Israel's borders before the 1967 Arab-Israeli war, modified by negotiated swaps of land between the two sides. Netanyahu, in his comments, had said the 1967 borders were "indefensible" and had ignored Obama's inclusion of land swaps as part of the formula.

Administration officials have been open in their irritation at the prime minister's words. And Obama made clear that he believed his position had been mischaracterized. "Since questions have been raised, let me repeat what I actually said on Thursday - not what I was reported to have said," he said.

He insisted that he does not want Israel pared back to the state that existed before the 1967 war. Israel must be able to "defend itself - by itself - against any threat," he said. In the end, the Middle East map will look different from "the one that existed on June 4, 1967," the day before the war began, he said.

"That's what mutually agreed-upon swaps mean," Obama added. "It is a well-known formula to all who have worked on this issue for a generation. It allows the parties themselves to account for the changes that have taken place over the last 44 years."

His words appeared to have reassured many in the audience, who applauded repeatedly, suggesting that Obama will pay little, if any, domestic political price for the quarrel with Netanyahu.

Netanyahu sounded a cooperative note as well, saying he appreciates Obama's "past and present efforts" at peace. Netanyahu addresses a joint session of Congress on Monday.

But given the zero-sum nature of Middle Eastern politics, Obama's emphasis on the land-swap component of his formula drew objections from the Palestinian side. "We were happier three days ago, before hearing his explanation," said Nabil Shaath, a senior Palestinian official. "He simply dismissed today any chance of going back to 1967 borders."

After Thursday's speech, Palestinian leaders - who for years have been calling for peace talks based on 1967 borders with swaps - expressed cautious optimism. Saeb Erekat, the former chief Palestinian negotiator, even hinted that if Netanyahu embraced Obama's framework, Palestinians might return to the negotiating table.

But after Sunday's address, Shaath said Obama focused too heavily on preserving Israel's security needs and respecting Israeli desire to maintain West Bank settlements, while saying nothing about Palestinian hot-button issues, such as having East Jerusalem as a capital and the right of return for refugees. Indeed, Obama's address Sunday was silent on those issues.

A White House senior adviser gave some insight into why the president chose this moment to lay out a specific formula for a peace accord. The aide, speaking on condition of anonymity, said that talks between the Israelis and Palestinians have stalled in part because "there was no clear foundation for them."

"The principles he [Obama] described on security and territory can provide a strong foundation for when talks do start," the aide said.