WASHINGTON — It was just a phrase at the end of President Obama’s news conference on Tuesday, but it was a stark reminder of a far-reaching shift in how the United States views the Israeli-Palestinian conflict, and how aggressively it might push for a peace agreement.

When Mr. Obama declared that resolving the long-running Middle East dispute was a “vital national security interest of the United States,” he was highlighting a change that has resulted from a lengthy debate among his top officials over how best to balance support for Israel against other American interests.

This shift, described by administration officials who did not want to be quoted by name when discussing internal discussions, is driving the White House’s urgency to help broker a Middle East peace deal. It increases the likelihood that Mr. Obama, frustrated by the inability of the Israelis and the Palestinians to come to terms, will offer his own proposed parameters for an eventual Palestinian state.

Mr. Obama said conflicts like the one in the Middle East ended up “costing us significantly in terms of both blood and treasure” — drawing an explicit link between the Israeli-Palestinian strife and the safety of American soldiers as they battle Islamic extremism and terrorism in Iraq, Afghanistan and elsewhere.

Mr. Obama’s words reverberated through diplomatic circles in large part because they echoed those of Gen. David H. Petraeus, the military commander overseeing America’s wars in Iraq and Afghanistan. In recent Congressional testimony, the general said that the lack of progress in the Middle East created a hostile environment for the United States. He has denied reports that he was suggesting that soldiers were being put in harm’s way by American support for Israel.

But the impasse in negotiations “does create an environment,” he said Tuesday in a speech in Washington. “It does contribute, if you will, to the overall environment within which we operate.”

The glimmers of daylight between United States and Israeli interests began during President George W. Bush’s administration, when the United States became mired in wars in Iraq and Afghanistan. Three years ago, Condoleezza Rice, then secretary of state, declared during a speech in Jerusalem that a peace deal between Israel and the Palestinians was a “strategic interest” of the United States. In comments that drew little notice at the time, she said, “The prolonged experience of deprivation and humiliation can radicalize even normal people.”

But President Bush shied away from challenging Israeli governments.

The Obama administration’s new thinking, and the tougher policies toward Israel that could flow from it, has alarmed American Jewish leaders accustomed to the Bush administration’s steadfast support. They are not used to seeing issues like Jewish housing in the West Bank or East Jerusalem linked, even by implication, to the security of American soldiers. Some fret that it raises questions about the centrality of the American alliance with Israel, which the administration flatly denies.

“In the past, the problem of who drinks out of whose well in Nablus has not been a strategic interest of the United States,” said Martin S. Indyk, a former United States ambassador to Israel and the vice president and the director of foreign policy at the Brookings Institution. He said there was an interest now because of the tens of thousands of troops fighting Islamist insurgencies abroad at the same time that the United States was trying to curb Iran’s nuclear ambitions.

“Will resolving the Palestinian issue solve everything?” Mr. Indyk said. “No. But will it help us get there? Yes.”

The administration’s immediate priority, officials said, is jump-starting indirect talks between Israelis and Palestinians. There is still a vigorous debate inside the administration about what to do if such talks were to go nowhere, which experts said is the likeliest result, given the history of such negotiations. Some officials, like Gen. James L. Jones, the national security adviser, advocate putting forward an American peace plan, while others, like the longtime Middle East peace negotiator Dennis B. Ross, who now works in the National Security Council, favor a more incremental approach.

Last week, National Security Council officials met with outside Middle East experts to discuss the Arab Israeli conflict. Two weeks before, General Jones and Mr. Obama met with several national security advisers from previous administrations and discussed putting forward an American proposal, even though it would put pressure on both Israel and the Palestinians.

Several officials point out that Mr. Obama has now seized control of Middle East policy himself, particularly since the controversy several weeks ago when Israeli authorities announced new Jewish housing units in Jerusalem during a visit to Israel by Vice President Joseph R. Biden Jr. Mr. Obama, incensed by that snub, has given Prime Minister Benjamin Netanyahu a list of demands, and relations between the United States and Israel have fallen into a chilly standoff.

“The president is re-evaluating the tactics his administration is employing toward Israel and the entire Middle East,” said Robert Wexler, a former Democratic congressman who resigned in January to lead the Center for Middle East Peace, a Washington-based nonprofit institution that is working for a peace agreement.

“I don’t think that anybody believes American lives are endangered or materially affected by the Israeli-Palestinian conflict,” said Mr. Wexler, who has close ties to administration officials. “That’s an oversimplification. However, you’d have to have blinders on not to recognize that there are issues in one arena that affect other arenas.”

For their part, administration officials insist that their support for Israel is unwavering. They point to intensive cooperation between the American and Israeli militaries, which they say has allowed Israel to retain a military edge over its neighbors.

The sense of urgency in Washington comes just as many Israelis have become disillusioned with the whole idea of resolving the conflict. Mr. Netanyahu’s right-wing coalition government has long been skeptical about the benefits of a peace deal with the Palestinians. But skepticism has taken root in the Israeli public as well, particularly after Israel saw little benefit from its traumatic withdrawal from Gaza in 2005.

Among American Jewish groups, there is less skepticism than alarm about the administration’s new direction. On Tuesday, the American Israel Public Affairs Committee, a powerful pro-Israel lobbying group, publicized letters to Secretary of State Hillary Rodham Clinton, signed by 76 senators and 333 House members, that implored the administration to defuse tensions.

In an open letter to Mr. Obama from the World Jewish Congress, the organization’s president, Ronald S. Lauder, asked, “Why does the thrust of this administration’s Middle East rhetoric seem to blame Israel for the lack of movement on peace talks?”

Mr. Lauder, who said the letter was scheduled to be published Thursday as an advertisement in The Washington Post and The Wall Street Journal, said he discussed the letter with Mr. Netanyahu and received his support before taking out the ad.