Mr Obama said the aim was to resolve the crisis diplomatically, but added that no option was off the table.
The US and Israel suspect that Iran is building a nuclear bomb. Iran says its programmes are for peaceful purposes.
Last November, the UN nuclear watchdog, the IAEA, said it had information suggesting Iran had carried out tests "relevant to the development of a nuclear explosive device".
Since then, the US and the EU have imposed a series of sanctions against Iran, including measures targeting the country's lucrative oil industry.
"I've been very clear - we're going to do everything we can to prevent Iran from getting a nuclear weapon and creating a nuclear arms race in a volatile region," Mr Obama told NBC in a live interview on Sunday.
He said Washington was working "in lockstep" with Israel, which was right to be very concerned about Iran's controversial activities.
Asked if he believed the Jewish state could launch a pre-emptive strike against Iran, Mr Obama said: "I don't think Israel has made a decision on what they need to do."
He declined to answer directly a question whether Washington would be consulted first, saying only that the US and Israel "have closer military and intelligence consultation... than we've ever had".
However, correspondents say that behind the scenes Washington is deeply alarmed by reports that Israel may strike Iran as early as April.
Such a move could drive up tensions in the Middle East as well as oil prices, analysts says, which would threaten the global economy and Mr Obama's re-election chances.
The US president said his country had "a very good estimate" of when Iran could complete a nuclear weapon.
But knowledge of Tehran's internal decision-making was not as clear, he said.
"Do we know all of the dynamics inside of Iran? Absolutely not,'' Mr Obama said. "Iran itself is a lot more divided now than it was. Knowing who is making decisions at any given time inside of Iran is tough.''
Mr Obama also said there was no evidence that the Iranians had "intentions or capabilities" to strike US targets in retaliation.
He stressed the US was attempting to resolve the showdown diplomatically but that the country had done extensive planning on all options.
"We are prepared to exercise these options should they arise,'' Mr Obama said during the interview.