Jerusalem - In a much-anticipated visit laden with symbols of friendship and words of assurance, President Barack Obama and Prime Minister Benjamin Netanyahu attempted to set aside past differences Wednesday and project a united front over how to tackle the threat of Iran's purported nuclear weapons program and other regional challenges.

But even as they tried to strike a more conciliatory tone, the two leaders stuck to sharply different timetables for potentially taking military action. Obama said Iran was at least a year away from developing a nuclear bomb, while Netanyahu warned that the Islamic Republic must be stopped sooner.

Nevertheless, the men displayed a measure of personal rapport that has been lacking in previous encounters, with Obama offering a tribute to Netanyahu's slain brother that nearly moved the prime minister to tears.

And though there appeared to be no substantive change in their positions, Netanyahu offered one of his strongest statements yet of confidence in Obama's commitment to Israel's security.

"I'm absolutely convinced that the president is determined to prevent Iran from getting nuclear weapons," Netanyahu said, though he added his oft-stated declaration that Israel reserves the right to defend itself.

Reassuring Netanyahu, and, perhaps more important, the Israeli public, is a major goal of the trip, whose official slogan is "Unbreakable Alliance." Obama called the U.S. commitment to Israel's security a "solemn obligation" and said his administration would ensure that $200 million earmarked for Israel's Iron Dome missile defense system this year would not be threatened by U.S. budget cuts.

"We will do what is necessary to prevent Iran from getting the world's worst weapons," he said. "Israel's security is guaranteed because it has a great deal on its side, including the unwavering support of the United States of America."

He vowed to maintain Israel's qualitative military edge in the Middle East so it can "defend itself, by itself, against any threat."

The two agree that Iran should not be allowed to develop a nuclear bomb and that military force might be necessary to stop it. But there is a long-standing dispute between them over exactly when to set the deadline for a military strike.

Netanyahu, who last year challenged Obama to publicly announce his "red line" for Iran, seeks an earlier deadline so Israel might still have the option to launch a unilateral attack in the event the U.S. does not take action. "Whatever time is left, there's not a lot of time," he said Wednesday.

With its superior weapons capabilities and military, the U.S. believes it can wait longer, and Obama wants to give economic and diplomatic sanctions more time.

In one of the lighter moments of the president's welcoming ceremony at Ben Gurion International Airport near Tel Aviv, Obama was momentarily unsure of which direction to walk and was told to follow red lines marked on the tarmac. "He's always talking to me about red lines," Obama joked, referring to Netanyahu's warning.

Despite the leaders' lingering differences, concern about a unilateral Israeli strike has receded in recent months, partly because Iran has buried many of its nuclear facilities so deep that they will be difficult for Israel to reach by itself.

In addition, after Israel's national election in January, Netanyahu is weaker politically. His new defense minister, Moshe Yaalon, has voiced skepticism about Israel striking Iran without U.S. support.

Another shared concern is the growing unrest in Syria, which borders Israel, and allegations that the embattled government of President Bashar Assad has used chemical weapons against its population.

Obama said his administration was still studying reports that Assad's military had used the banned weapons on civilians in a village in northern Syria. Israel has said it believes the reports are true. Assad's government says the chemical attack was launched by anti-Assad rebels.

Obama, who has dismissed the idea that the Syrian opposition launched a chemical attack, said that his administration viewed the use of such weapons as a "game-changer" but that "having the facts before you act is very important."

Neither man spoke extensively about the Palestinian conflict, though Netanyahu expressed hope that the visit would help "turn a page in our relations with the Palestinians" and reopen peace negotiations.

Obama, who will meet with Palestinian Authority President Mahmoud Abbas on Thursday, promised he would have more to say about the issue during a speech to Israeli students in Jerusalem.

The start of his visit was heavy on diplomatic pleasantries, with lots of Israeli and American flags, and children singing and posing for pictures with soldiers.

Obama's speech during the welcome ceremony was notable for what he did not say, avoiding mention of the Palestinian conflict, settlement construction, Iran or any other sensitive issues.

Instead, he began by acknowledging the Jewish people's 3,000-year connection to the Holy Land and emphasizing the shared values of Americans and Israelis. Such comments were designed to ease the minds of Israelis, many of whom have never fully warmed to the president and felt snubbed by his failure to visit the nation during his Cairo trip in 2009.

Obama brought with him a magnolia tree, a surprise gift for President Shimon Peres as a symbol of the nations' eternal bond. The two participated in a planting ceremony in Peres' garden, although Israeli agriculture officials later said the tree would be uprooted and inspected because it violated quarantine rules.

As expected, Obama and Netanyahu took strides to display warmth and informality, a marked difference from the coolness of their previous joint appearances. Both casually removed their jackets to reveal matching blue ties during a tour of Israel's Iron Dome system in the midday heat. The Iron Dome was designed in Israel and partly funded by the United States.

They joked about each other's upcoming budget challenges. Netanyahu offered to give Obama an incognito tour of Tel Aviv bars and cafes.

The carefully orchestrated schedule went much as planned except for a brief clamor over the breakdown of one of Obama's limousines as the motorcade was being assembled to pick up the president's party. It was towed away and replaced with a backup.

According to the Israeli press, the limo broke down after its tank was filled with the wrong kind of gasoline.