Standing on Israeli soil, presumptive U.S. presidential candidate Mitt Romney on Sunday declared Jerusalem to be the capital of the Jewish state and said the United States has “a solemn duty and a moral imperative” to block Iran from achieving nuclear weapons capability.

“It is a deeply moving experience to be in Jerusalem, the capital of Israel,” Romney said in a press conference on the Ninth of Av with the Old City as his backdrop.

Romney’s declaration falls in line with the Jerusalem Embassy Act—passed by Congress in 1995—which calls for Jerusalem to be recognized as the capital of Israel, but has never been implemented. Presidents Bill Clinton, George W. Bush, and now Barack Obama have viewed it as a congressional infringement on the executive branch’s constitutional authority over foreign policy, and their administrations have consistently exercised presidential authority to waive the law based on national security interests.

White House Deputy Press Secretary Josh Earnest on Monday said that Romney’s comments about Jerusalem were in contradiction to previous administrations, “both Democratic and Republican.”

A reporter at a White House briefing session pushed Earnest on the issue of Romney’s comments, posing the question: “Governor Romney declared flatly that Jerusalem is the capital of Israel. And I’m wondering, what does the White House [think]—does that undermine the administration’s position? Is that a comment that the administration would have preferred gone unsaid? How does the administration view that?”

In his response, Earnest said, “Well, our view is that that’s a different position than this administration holds. It’s the view of this administration that the capital [of Israel] is something that should be determined in final status negotiations between the parties. I’d remind you that that’s the position that’s been held by previous administrations, both Democratic and Republican. So if Mr. Romney disagrees with that position, he’s also disagreeing with the position that was taken by presidents like Bill Clinton and Ronald Reagan. So, again, if he does disagree with that position, I would leave it to him to explain it.”

In his speech on Sunday, Romney also stressed that a different American response was needed to confront the danger posed by Iran to Israel. “Make no mistake: the ayatollahs in Tehran are testing our moral defenses. They want to know who will object, and who will look the other way,” he said. “My message to the people of Israel and the leaders of Iran is one and the same: I will not look away; and neither will my country.”

Romney warned of Iran’s nuclear progress and underscored the importance of stopping the regime. “Today, the regime in Iran is five years closer to developing nuclear weapons capability. Preventing that outcome must be our highest national security priority.

“It would be foolish not to take Iran’s leaders at their word. They are, after all, the product of a radical theocracy. It is Iran that is the leading state sponsor of terrorism and the most destabilizing nation in the world,” he said.

Underscoring U.S. support for Israel against Iran, Romney added, “We recognize Israel’s right to defend itself, and that it is right for America to stand with you. We have a solemn duty and a moral imperative to deny Iran’s leaders the means to follow through on their malevolent intentions.”

In what appeared to be an attempt to distinguish himself from Obama, who has trumpeted his military support for Israel as being unparalleled to that of previous U.S. administrations, Romney said, “standing by Israel does not mean with military and intelligence cooperation alone. We cannot stand silent as those who seek to undermine Israel, voice their criticisms. And we certainly should not join in that criticism. Diplomatic distance in public between our nations emboldens Israel’s adversaries.”

The presidential election hovered over the speech. Romney’s declaration that Jerusalem is Israel’s capital was matter-of-fact and in keeping with claims made by Israeli governments for decades, even though the U.S., like other nations, maintains its embassy in Tel Aviv.

He did not say if he would order the embassy moved if he wins the White House, but strongly suggested so in a CNN interview.

“My understanding is the policy of our nation has been a desire to move our embassy ultimately to the capital (Jerusalem),” he said, adding, “I would only want to do so and to select the timing in accordance with the government of Israel.”

Earlier Sunday, Romney and his wife, Ann, were given a presidential welcome by Prime Minister Benjamin Netanyahu who hosted the two at his official residence, and gave Romney an embrace befitting of close friends.

Ahead of his meeting with Netanyahu, Romney, who arrived in Israel Saturday night for a two-day visit, toured Jerusalem, visited the Western Wall, and put a note in its cracks, according to the well-known tradition. Ann Romney even fasted on Sunday in solidarity with the Jewish people on its day of national mourning, Tisha B’Av.

During his meeting with Netanyahu, Romney said, “We have a relationship between our nations which spans many years, and at the same time, is one based not just upon mutual interests, but also shared values. Your perspectives with regards to Iran and its effort to become a nuclear-capable nation are ones which I take with great seriousness and look forward to chatting with you about further actions that we can take to dissuade Iran from their nuclear folly.”

Netanyahu replied, “Governor Romney, Mitt, it’s a pleasure to welcome you here. I have to say that I heard some of your remarks a few days ago—you said that the greatest danger facing the world is of the Ayatollah regime possessing nuclear weapons capability. Mitt, I couldn't agree with you more, and I think it's important to do everything in our power to prevent the ayatollahs from possessing the capability. We have to be honest and say that all the sanctions and diplomacy so far have not set back the Iranian program by one iota. And that’s why I believe that we need a strong and credible military threat, coupled with the sanctions, to have a chance to change that situation.”

In a meeting with President Shimon Peres, which centered on the Iranian threat, Romney said, “Like you we are concerned about Iran developing nuclear capability and feel that it is inconceivable that Iran will become a nuclear armed nation. The threat this would have against Israel, the region and the world is unacceptable.”

Romney also met with Palestinian Authority Prime Minister Salam Fayyad. Following his statement that Jerusalem was Israel’s capital, chief Palestinian Authority negotiator Saeb Erekat was quoted by Israel Radio as saying, “Mitt Romney’s words are damaging, they harm peace, stability and security. … We reject these statements completely.”