"We think that it would take over a year or so for Iran to actually develop a nuclear weapon," Obama told Israel's Channel 2 in an interview ahead of Obama's three-day trip beginning Wednesday that will also take him to the West Bank and Jordan.
Israeli Prime Minister Binyamin Netanyahu, who will meet with Obama in Jerusalem Wednesday, told the United Nations in September Israel believed Iran would be close to nuclear weapons capability in the spring or summer of this year.
"Obviously we don't want to cut it too close," Obama said in the interview broadcast Thursday.
"So when I'm consulting with Bibi [Netanyahu's popular nickname, a holdover from his childhood], as I have over the last several years on this issue, my message to him will be the same as before: If we can resolve this diplomatically, that is a more lasting solution. But if not, I continue to keep all options on the table."
When asked if he would order an attack on Iran if diplomatic means failed, Obama said, "When I say all options are on the table, all options are on the table, and the United States obviously has significant capabilities."
He said Washington's goal was to ensure "Iran does not possess a nuclear weapon that could threaten Israel or trigger an arms race in the region that would be extremely dangerous."
Netanyahu, who repeated Thursday he was impatient with Washington's Iran strategy, has said a nuclear-armed Iran an existential threat to Israel. Iran has denied the Holocaust and called for Israel's destruction.
Iran insists its uranium-enrichment program is for peaceful purposes to produce energy and medical isotopes -- a claim Israel and many Western countries reject.
On the diplomatic process with Palestinian officials, Obama said nothing of coming to the region with a peace initiative or an outline of how to move the process forward. He said his goal was to listen to both sides and hear their strategies and visions.
White House deputy national security adviser Ben Rhodes confirmed in a news briefing "this visit is not about trying to lay down a new initiative or complete our work on a particular issue."
Israeli-Palestinian peace discussions ended in 2010 amid mutual bitterness and Palestinian anger over Israeli settlement expansion in the occupied West Bank.
Israel has expanded its West Bank settlements in spite of 1993's Oslo Accords, an interim agreement that said neither side would change the West Bank status until "permanent status negotiations" began toward a final agreement.
Israeli settlements and other major issues, such as Jerusalem, Palestinian refugees and security and borders, were to be decided at those permanent status negotiations.
Obama told Channel 2 the only path forward was for Israelis and Palestinians to get back into negotiations.
He said he intended to explore during his visit "whether that can happen soon or whether there needs to be further work on the ground."
Obama said he would tell Palestinian Authority President Mahmoud Abbas in Ramallah Thursday Palestinian attempts to achieve statehood recognition at the United Nations would fail, and he would tell Netanyahu Israel should focus on strengthening the authority's moderate leadership.
Issues such as West Bank settlements should be "viewed through the lens of, is this making it easier or harder for Palestinian moderates to sit down at the table?" Obama said he planned to suggest to Netanyahu.
He called his relationship with Netanyahu -- a relationship widely perceived as strained -- a "terrific, business-like relationship."
"I've met with Bibi more than any other world leader one-on-one," he said. "He is very blunt with me about his views on issues, and I am very blunt with him about my views on issues. And we get stuff done. We could not coordinate militarily or on the intelligence side had it not been for our capacity to work together."
The centerpiece of Obama's visit is expected to be a nationally televised address to Israelis, mainly students, Thursday, Rhodes said.
The speech is expected to "focus on the nature of the ties between the United States and Israel, the broad agenda that we work on together on security, on peace, on economic prosperity," Rhodes said.
"And I think he'll have a chance to speak to the future of that relationship, so discussing not just the nature of the challenges that we face today, but where the United States and Israel are working to move together as we head into the future of the 21st century."
Obama also plans to meet with Jordan's King Abdullah II in Amman Friday.