(Reuters) - President Barack Obama said Sunday that Israel has not yet decided how to respond to concerns about Iran's nuclear program and said there was no evidence that Iran has the intentions or capabilities to wage attacks on U.S. soil.

Asked in an NBC interview whether Israel was set to attack Iran, Obama said: I don't think that Israel has made a decision on what they need to do. I think they, like us, believe that Iran has to stand down on its nuclear weapons program, adding Israel and the United States would work in lockstep on Iran.

Obama, who is up for re-election in November, has ended the U.S. war in Iraq and is seeking to wind down combat in Afghanistan amid growing public discontent about war spending at a time when the economy remains weak.

The Democrat made clear on Sunday that he would not like to see more fighting in the oil-producing Persian Gulf region.

Any kind of additional military activity inside the Gulf is disruptive and has a big effect on us. It could have a big effect on oil prices, we've still got troops in Afghanistan, which borders Iran, and so our preferred solution here is diplomatic, he said.

Republican Mitt Romney, the top contender to oppose Obama in the presidential election, said he would start his presidency by imposing far tougher sanctions on Iran and back up American diplomacy with a very credible military option.

Tehran says its nuclear program is meant to produce energy, not weapons, but has not responded to the latest Western overtures for talks and has threatened to retaliate against U.S. and European sanctions affecting its finances and oil sales.

In the NBC interview, Obama stressed he was not taking any options off the table to stop Iran from becoming a nuclear power. We're going to do everything we can to prevent Iran from getting a nuclear weapon and creating an arms race - a nuclear arms race - in a volatile region, he said.

(Reporting by Laura MacInnis and Aruna Viswanatha; Editing by Stacey Joyce)