Washington (CNN) -- Mitt Romney seeks to assure Israel and Iran, as well as Jewish voters in the United States, that he will be tougher against Iran's nuclear ambitions than President Barack Obama.
So far, though, the main differences on the issue between the presumptive Republican nominee and the president he hopes to defeat in the November election involve tone and nuance more than substance.
In two high-profile speeches in the past week, Romney has tried to position himself as a better friend to Israel than Obama by pledging full support for any steps necessary to prevent Iran from becoming a nuclear state.
Calling the issue America's "highest national security priority," the former Massachusetts governor said Sunday in Jerusalem that "we recognize Israel's right to defend itself, and that it is right for America to stand with you."
Meanwhile, a top Romney adviser on foreign policy told reporters Sunday that Romney would respect a decision by Israel to "take action on its own in order to stop Iran" from developing nuclear capability -- code for a possible Israeli military strike against Iranian nuclear facilities.
The adviser, Dan Senor, said Romney was not advocating war with Iran, only making clear what the options were should diplomacy fail. He later sought to clarify his comment by noting Romney hoped diplomatic efforts would succeed.
Romney's stance is "almost identical" to Obama's position, which seeks increased international pressure on Iran while keeping a military option "on the table," noted Martin Indyk, a former U.S. ambassador to Israel during the Clinton administration who now is foreign policy director at the Brookings Institution.
"It's hard to see what the difference is, since Gov. Romney and his spokesman make it clear that sanctions and negotiations would be tried and force should be kept on the table as a last resort," Indyk told CNN on Monday.
Even Romney seemed to recognize the similarity, telling CNN in an interview broadcast Monday that "our president has said and I have said that it is unacceptable for Iran to become nuclear."
"And that would mean that if all other options were to fail -- and they have not all been exercised, they've not all been executed at their most extreme level -- but if all other options -- diplomatic, political, economic -- fail, then a military option is one which would be available to the president of the United States," Romney told CNN's Wolf Blitzer.
Romney's three-nation trip to key U.S. allies Great Britain, Israel and Poland has shifted the election campaign spotlight to foreign policy, with particular focus on thorny issues such as the Middle East conflict and Iran.
While he directly criticized Obama in last week's speech to American war veterans, Romney has avoided similar attacks against the president while on foreign soil. At the same time, he sought to distinguish himself from Obama on some specific issues.
For example, Romney made a point of calling Jerusalem the capital of Israel, though he conceded in the interview with CNN that the issue must be resolved through negotiations between Israel and the Palestinians -- the position of Obama and previous presidents.
Romney also made a point in both speeches of calling for a halt of all nuclear enrichment by Iran, aligning himself with Israel's insistence that Iran must have no nuclear capability.
To Indyk, that kind of pronouncement was something a candidate can say on the campaign trail that doesn't easily adapt to the realities of complex international negotiations.
He noted the United States and its negotiating partners in the so-called P5-plus-1 talks with Iran seek implementation of U.N. Security Council resolutions that call for Iran to cease its enrichment program.
While some form of limited enrichment could emerge from negotiations, the stated policy of the Obama administration for now is the same as what Romney declared, Indyk said.
"The view is different from the Oval Office than on the campaign trail," said Indyk, one of three authors of the recent book "Bending History: Barack Obama's Foreign Policy."
"If you're actually trying to negotiate an agreement which secures the bottom line -- that is to say that you put meaningful curbs on Iran's nuclear program such as they cannot procure nuclear weapons -- then you're going to have find some way to get to that," he added.
Another issue of contention between the campaigns has been whether the diplomatic efforts that include U.N. and other sanctions have made any progress.
Romney's team insists the negotiations and sanctions have proven fruitless and allowed Iran to continue to develop its enrichment capability in recent years.
Israeli Prime Minister Benjamin Netanyahu bolstered that argument by saying Sunday that "all the sanctions and diplomacy so far have not set back the Iranian program by one iota."
"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," he added.
Netanyahu is a longtime friend and former work colleague of Romney, but his relationship with Obama has been rocky. The Obama administration, while maintaining strong support for Israel's military and security, has adopted a more mediating role in the Middle East peace process that has chafed at times.
Defense Minister Ehud Barak noted the dynamic in an interview with CNN that was broadcast Monday.
"This administration under President Obama is doing in regard to our security more than anything that I can remember in the past," Barak said, later adding "it doesn't mean that we agree on everything."
Administration officials argue the president has built the foundation for an international coalition that is increasing pressure on Iran through sanctions.
Russia and China have supported Security Council measures against Iran, which was "not an insignificant development," noted Josh Earnest, the principal White House deputy press secretary.
Now, Earnest told reporters Monday, the Iranian regime is acknowledging the toll of sanctions and "starting to exhibit some signs of dissent within the ranks."
Indyk said Romney can make the point that Iran has made progress on nuclear enrichment despite Obama's diplomatic efforts, "but Obama has made progress against Iran, which I don't think is convenient for the Romney campaign to admit to."
He cited European oil sanctions on Iran, something Indyk said would have been "inconceivable" under the past two presidents.
Michele Flournoy, a former U.S. Defense Department official who co-chairs the Obama campaign's national security advisory committee, said last week that Pentagon planning for a possible military option in Iran is "incredibly robust."
"You look at our force posture in the region -- you know, it is very strong and well positioned," Flournoy told a Brookings Institution event on the candidates' foreign policy positions. "So, the military option is real. The president's judgment is that now is not yet the time, because there is still a chance, with further sanctions biting, for Iran to change its calculus."
Asked how much longer before a military strike might be necessary to prevent Iran from being able to enrich weapons-grade material, Flournoy said the intelligence community believes it will be "a year or more at a minimum."
At the same event, however, Romney's senior adviser for foreign and defense policy said the Obama administration offered "no credible threat of force."
"No one in Tehran or in the region feels that the Obama administration will use force," said Rich Williamson, a former ambassador and top official in several Republican administrations.
In the Jerusalem speech, Romney defended a hard-line stance on Iran as a deterrent to war, rather than a desire to start one.
"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," he said. "The opposite is true. We are the true peacemakers. History teaches with force and clarity that when the world's most despotic regimes secure the world's most destructive weapons, peace often gives way to oppression, to violence, or to devastating war."
The audience included influential American Jewish figures such as Sheldon Adelson, the Las Vegas casino magnate who donated $10 million to a pro-Romney super PAC. Asked what he thought of Romney's speech, Adelson gave a thumbs-up.
CNN's Jim Acosta and Rachel Streitfeld contributed to this report.