Mitt Romney stepped forcefully into a diplomatic stalemate here Sunday by calling on the United States and Israel to use “any and all measures” to lead the effort to prevent Iran from developing nuclear weapons.

In a speech delivered from a terrace overlooking the Old City of Jerusalem, Romney said the United States would support Israel’s efforts to defend itself, a principle President Obama has also endorsed. And the Republican presidential hopeful stopped short of asserting that he would support a unilateral military strike by Israel against Iran to stop Tehran from obtaining nuclear capability, though a top adviser said he would respect Israel’s right to take such action.

But as he has done throughout the campaign, he cast the Iranian threat in dire terms, using sharp language in an effort to differentiate his worldview from Obama’s.

“We must not delude ourselves into thinking that containment is an option,” Romney said. “We must lead the effort to prevent Iran from building and possessing nuclear weapons capability. We should employ any and all measures to dissuade the Iranian regime from its nuclear course, and it is our fervent hope that diplomatic and economic measures will do so.”

“In the final analysis, of course, no option should be excluded,” Romney continued. “We recognize Israel’s right to defend itself and that it is right for America to stand with you.”

The presumptive nominee delivered his address after a series of meetings with top Israeli and Palestinian officials and network television interviews. He visited the Western Wall in Jerusalem, one of Judaism’s holiest religious sites, where he left a prayer note in a crease in the wall as he marked the fasting holiday of Tisha B’av.

Sunday was a carefully choreographed day — campaign aides arrayed 64 alternating U.S. and Israeli flags to line the open-air speech venue, symbolizing the 64 years that Israel has existed — designed to help Romney broaden his appeal to Jewish American voters and other supporters of Israel, including evangelical Christians. Obama won the Jewish vote by a wide margin in 2008 and still holds an edge among the group in recent polling.

In his speech, Romney declared Jerusalem to be the capital of Israel. The United States does not recognize Jerusalem as Israel’s capital because it is claimed by Israelis and Palestinians. Israel occupied East Jerusalem, which includes the Old City, in the 1967 Middle East War and annexed it soon after — an act not recognized internationally.

The United States maintains its embassy in Tel Aviv, as do many other nations, and Romney’s remarks were a tacit criticism of White House press secretary Jay Carney, who last week told a pair of journalists who asked him to name Israel’s capital that they already knew the answer, declining to comment further.

In his remarks Sunday, Romney outlined a more aggressive U.S. posture toward the United States’ and Israel’s shared antagonists, but he did not offer any new policy specifics. Instead, he offered a historic survey of U.S.-Israel relations since the birth of the Jewish state in 1948 and pledged, as Obama has done as recently as Friday, an unconditional defense of Israel’s security.

The Iranian uranium-enrichment program consumed much of Romney’s address, during which he did not mention “Palestinians” or the need for a peace process based on the two-state model promoted by the United States.

There is little daylight between Romney’s policy approach to Iran and the policies Obama has pursued — a series of ever-tougher economic sanctions and occasional negotiation — although Romney used more heated rhetoric to describe the Iranian threat.

“It is sometimes said that those who are the most committed to stopping the Iranian regime from securing nuclear weapons are reckless and provocative and inviting war,” Romney said. “The opposite is true. We are the true peacemakers.”

Although he did not address campaign politics in his remarks, his roughly 36-hour trip to Israel has been overtly political.

Many of Romney’s biggest benefactors flew here from the United States for the occasion, including Las Vegas casino mogul Sheldon Adelson, who has pledged to give tens of millions of dollars to a pro-Romney super PAC.

Adelson sat behind Romney’s wife, Ann, during Sunday’s speech, while top Romney campaign fundraisers occupied the front rows. The campaign took donors on a private tour of historic sites, and many of them accompanied Romney to the Western Wall. New York lawyer Philip Rosen stood a few feet from the candidate as he tucked his prayer note into the wall.

Before he departs for Poland on Monday morning, Romney will hold a fundraiser at the King David Hotel. After coming under fire for saying it would ban reporters from the event, the campaign said Sunday that it would be open to the news media.

Romney’s speech came hours after one of his senior foreign policy advisers, Dan Senor, told reporters that Romney would support Israel’s right to launch a unilateral military strike against Iran.

The Obama administration has urged the Israelis to be patient while international sanctions against Iran are given time to work but has assured Prime Minister Benjamin Netanyahu that Israel has the right to act in its own national security interests. Some in the administration fear that an Israeli strike against Iran could ignite a regional war.

Defense Minister Ehud Barak issued a statement Saturday thanking Obama after he signed into law the previous day an act upgrading security ties with Israel, endorsing the concept of preserving Israel’s “qualitative military edge” in the region. But there was no such declaration of gratitude by Netanyahu. Obama’s step was widely seen as an attempt to parry Romney’s visit here.

On Sunday morning, a senior Israeli official denied a report in the Israeli newspaper Haaretz that Obama’s national security adviser, Thomas E. Donilon, had briefed Netanyahu during a recent visit on U.S. plans for a possible attack on Iran.

The report, which cited an unnamed senior American official, coincided with the start of Romney’s meetings and appeared to underline Obama’s readiness to use military force.

“Nothing in the article is correct,” said the Israeli official, who spoke on the condition of anonymity because of the sensitivity of the issue.

The report came at the start of a full day of official meetings designed for Romney to deepen his ties with Israeli leaders, including Netanyahu, a friend of Romney’s since they worked together as business consultants in the 1970s.

Romney met with Netanyahu on Sunday morning at the prime minister’s Jerusalem offices. After sundown, their families shared a private meal at Netanyahu’s home to break the holiday fast.

Although he spoke fondly of Romney, even playfully telling him that after so many decades “you still look young,” Netanyahu has avoided any remarks that could be construed as taking sides in the U.S. presidential campaign.

Zalman Shoval, a former Israeli ambassador to the United States and a Netanyahu adviser who attended the meeting with Romney, said Romney did not repeat past criticisms of Obama’s policies toward Israel or try to lay out a Middle East policy different from that of the administration.

“He was more in a listening mode than talking,” Shoval said.

The discussion also covered the perils of the upheaval in Syria and Israeli concerns about Syria’s chemical weapons stocks falling into the hands of the Iranian-backed Lebanese group Hezbollah, Shoval said. The Palestinian issue, he noted, “did not come up in the meeting.”

Scott Wilson in Washington contributed to this report.