JERUSALEM: President Barack Obama’s first Middle East tour, since he won the second term, started with the long-awaited visit to Israel Wednesday where he pledged an “eternal” alliance with the Jewish state.

During his three-day visit, Obama will also hold talks in Ramallah with Palestinian President Mahmoud Abbas and travel to Jordan before returning home Saturday.

Eager to reassure an anxious ally, Obama promised to work closely with Israel and do whatever was necessary to keep Iran from obtaining nuclear arms, “the world’s worst weapons.”

Obama, meeting with Israeli Prime Minister Benjamin Netanyahu, said of Iran’s nuclear ambitions: “We prefer to resolve this diplomatically and there is still time to do so.” But he added that “all options are on the table” if diplomacy falls short.

“The question is, will Iranian leadership seize that opportunity,” he added. The president said Iran’s past behavior indicates that “we can’t even trust yet, much less verify.”

Netanyahu, at Obama’s side for a joint news conference, said that while he appreciated U.S. efforts to thwart Iran’s pursuit of nuclear weapons through diplomacy and sanctions, those tools “must be augmented by a clear and credible threat of military action.”

“I am absolutely convinced that the president is determined to prevent Iran from getting nuclear weapons,” Netanyahu said. “I appreciate that. I appreciate the fact that the president has reaffirmed, more than any other president, Israel’s right and duty to defend itself by itself against any threat.”

The Israeli leader said that he and Obama agree that it would take Iran about a year to manufacture a nuclear weapon. Obama said there is “not a lot of light, a lot of daylight” between the two leaders in intelligence assessments about Iran, and Netanyahu concurred.

Although preventing Iran from developing a nuclear weapon is a priority of both Israel and the United States, Netanyahu and Obama have differed on precisely how to achieve that.

Israel repeatedly has threatened to take military action should Iran appear to be on the verge of obtaining a bomb. The U.S. has pushed for more time to allow diplomacy and economic penalties to run their course, though Obama insists military action is an option.

Obama also took note of the difficult way forward in the broader quest for Middle East peace, acknowledging that in recent years “we haven’t gone forward, we haven’t seen the kind of progress that we would like to see.”

The president said he came to the region principally to listen, and hoped to return home with a better understanding of the constraints and “how the U.S. can play a constructive role.”

Netanyahu, for his part, said he was willing to set aside preconditions in future talks with the Palestinians, adding that it was time to “turn a page in our relations.”

Obama’s visit to Israel, from the start, has been designed to send a message of reassurance to a key ally.

At an extravagant welcoming ceremony, Obama sounded a message that “peace must come to the Holy Land” and that such a goal could not be achieved at Israel’s expense. U.S. backing for Israel will be a constant as the Middle East roils with revolution and Iran continues work on its nuclear program, he said.

“The United States is proud to stand with you as your strongest ally and your greatest friend,” Obama said after landing at Tel Aviv’s Ben Gurion International Airport.

He called his visit “an opportunity to reaffirm the unbreakable bonds between our nations, to restate America’s unwavering commitment to Israel’s security, and to speak directly to the people of Israel and to your neighbors.”

Seeking to alter a perception among many Israelis that his government had been less supportive than previous U.S. administrations, Obama declared the U.S.-Israeli alliance “eternal.”

“It is forever,” he said to applause as Israeli and U.S. flags fluttered in a steady breeze under clear, sunny skies. Even before leaving the airport for Jerusalem, Obama offered a vivid display of the U.S. commitment to Israeli security by visiting a missile battery that is part of Israel’s Iron Dome defense from militant rocket attacks.

Netanyahu, who sparred frequently with Obama over the course of the U.S. president’s first term, praised the president.

“Thank you for standing by Israel at this time of historic change in the Middle East,” he said. “Thank you for unequivocally affirming Israel’s sovereign right to defend itself by itself against any threat.”

Thursday, Obama plans to speak to Israeli university students and again renew U.S. security pledges as Israel seeks to counter threats from Iran.

In the West Bank town of Ramallah, Obama will assure Abbas that an independent Palestinian state remains a U.S. foreign policy and national security priority.

As Israelis warmly greeted Obama, Palestinians held several small protests in the West Bank and Gaza.