US presidential candidate Mitt Romney has told an Israeli audience in Jerusalem that the United States has "a solemn duty and a moral imperative" to block Iran from achieving nuclear weapons capability.
Romney's speech on Sunday came at the mid-point of a three-nation overseas journey designed to burnish his foreign policy credentials and highlight his ability to lead on the world stage.
"The conduct of Iran's leaders gives us no reason to trust them with nuclear material," Romney said, adding: "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.
"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."
The US, many of its European allies and Israel say Iran is trying to build a nuclear weapon. Iran says its uranium enrichment is part of a peaceful domestic nuclear programme for energy and medical research.
So far all attempts to negotiate an end to the enrichment programme have failed.
Israel fears that Iran soon will have moved its enrichment facilities into impregnable underground locations, meaning time is running out to destroy them with aerial bombing.
Romney said the US supported Israel's right to defend itself but would not expand on his remarks, saying he would hold to US political tradition of not differing with positions taken by a sitting government.
President Barack Obama has sought to dissuade Israel from a unilateral attack on Iran to allow time for tough sanctions to take a toll on the Islamic Republic's economy and further isolate the country.
Obama has said the US holds open the option of military operations against Iran but has insisted now is not the time for an attack, either by the US or Israel.
While Romney refused to criticise Obama's policy directly, he insists he would be much tougher on Iran. His policy declarations, however, show little, if any, difference from those of Obama.
But by raising the issue in Israel, which sees Iran as an existential threat, Romney was obviously looking for support from Jewish and evangelical Christian voters in the United States.
Romney, who received a warm welcome from Prime Minister Binyamin Netanyahu, has said he has a "zero tolerance" policy toward Iran obtaining the capability to build a nuclear weapon.
Obama also has affirmed the right of Israel to defend itself, but in contrast to Romney, he has warned of the consequences of an Israeli strike on Iran.
"Already, there is too much loose talk of war," Obama told the American Israel Public Affairs Committee, an influential pro-Israel lobbying group, in March.
"Now is the time to let our increased pressure sink in and to sustain the broad international coalition we have built."
Romney's embrace of Israel was on display on Sunday as he met with leaders and visited the Western Wall in Jerusalem, one of the holiest sites in Judaism.
Wearing a yarmulke, the candidate was mobbed by worshippers as he walked down to pray and place a note into one of the wall's crevices.
Earlier, Netanyahu welcomed Romney as "a representative of the United States" and told the Republican that he agrees with his approach to the Iranian nuclear threat.
"Mitt, I couldn't agree with you more," Netanyahu said.
"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," Netanyahu said.
Romney also hailed Jerusalem as the capital of Israel, in an apparent endorsement of a position held by Israel but never accepted by the international community.
"It is a deeply moving experience to be in Jerusalem, the capital of Israel," the Republican challenger said at the outset of the speech on Sunday.
Senior Palestinian negotiator Saeb Erakat said Romney's declarations about the city were "harmful to US interests in the Middle East".
"It is unacceptable and we completely reject it," Erekat said.
The trip is a chance for Romney to draw implicit contrasts with Obama and demonstrate how he would lead America on the world stage.
But Romney arrived in Jerusalem on Saturday night after a difficult few days in Britain, where he made the mistake of criticising the host country's preparations for the Olympic Games.
The gaffe undermined the stated goal of his weeklong trip to Britain, Israel and Poland - emphasising America's ties with longstanding allies.
On Monday morning, Romney will be attending a high-dollar campaign fundraiser at the King David Hotel in Jerusalem for American supporters in Israel.
The Romney campaign has reversed course and now will let reporters cover his remarks to donors, reversing an earlier ban on coverage.
One of those expected to attend is Sheldon Adelson, the American casino mogul who's pledged to spend more than $100 million to defeat Obama.
Donors at the event were asked to contribute $50,000 or to raise $100,000. Romney advisers say the event is expected to raise more than $1m.