Hints, warnings and coded political signals from Israel about a possible strike against Iran are piling pressure on US President Barack Obama and fueling an explosive election year debate.

Obama personally weighed into the churning speculation on Sunday, saying he did not believe Israel had yet made a decision to attack underground Iranian nuclear facilities it views as a threat to its existence.

And the president forcibly argued that "unprecedented" tougher sanctions on Iran were having a painful impact.

"They are feeling the pinch. They are feeling the pressure," Obama told NBC.

Speculation about a strike on Iran's nuclear program hit new heights when Israeli intelligence writer Ronen Bergman concluded a week ago in a New York Times magazine article that Israel would attack Iran this year.

Israeli Defense Minister Ehud Barak sent reverberations through Washington when he called for timely but unspecified action against Iran, adding, "Whoever says 'later' might find that 'later' is too late."

Then, Washington Post columnist David Ignatius set off alarm bells by writing that Defense Secretary Leon Panetta believed there was a "strong likelihood that Israel will strike Iran in April, May or June."

"President Obama and Panetta are said to have cautioned the Israelis that the United States opposed an attack," Ignatius wrote.

Panetta refused to elaborate, but did not contradict the article, deepening intrigue over Israel's next move.

Even if it has not decided to act, analysts say Israel may see martial rhetoric as a way to press for more non-military pressure on Iran.

"Israel is effectively pressing the US Congress and the president to pass more sanctions and implement those that have passed as quickly as possible," said Cliff Kupchan, an Iran specialist with the Eurasia Group risk consultancy.

Kupchan said that the feeling that Israel could attack may also be seen as an attempt to force Tehran back to nuclear talks.

Some observers in Washington calculate that Israel may be bluffing because previous military strikes, like the suspected assault on a Syrian nuclear reactor in 2007, were not preceded by saber rattling.

Israeli leaders may also not yet be ready to unleash the dire consequences of an attack, which could include reprisal missile strikes by Iran and action by allied terror groups against the Jewish state.

But no one here can say categorically what Israel plans to do.

The saga has again exposed divisions between the White House and Prime Minister Benjamin Netanyahu's government, which may be on show again when the Israeli leader visits Washington next month.

The US administration has signaled that it believes the last resort scenario that would see a strike on Iranian nuclear sites has not yet been reached.

"Israel has indicated that they're considering this... we have indicated our concerns," Panetta told reporters last week.

Iran expert Trita Parsi said that as the White House steps up pressure on Iran, bellicose rhetoric from Israel could be helpful if it spooks Tehran over the possibility of an attack.

But Parsi, author of a new book on Obama's Iran policy called "A Single Roll of the Dice," warned that using the implied threat of war if sanctions do not stop the nuclear program was a large gamble.

"The administration knows that there are moving parts which it does not control," Parsi said, referring to uncertainty about how Israel or Iran could react in moments of high crisis.

A unilateral military strike by Israel would have deep strategic consequences for the United States and grave political implications for Obama.

Washington would almost certainly be drawn into a new conflagration in the Middle East at a time when Obama wants to claim credit for getting troops home from Iraq.

Oil prices would shoot up, crimping the US economic recovery just as it speeds up and slowing jobs growth that Obama needs to win reelection.

Israeli leaders, keen students and practitioners of US politics, understand this, and know Obama may be vulnerable to pressure during his reelection bid.

Daniel Levy of the New America Foundation said the tough talk from Israel and sense of crisis had not been triggered by sudden advances by Iran on its nuclear program -- but politics.

"The only reason why that this is anywhere near the top of the agenda where it is now is because of the American presidential election," said Levy.

"(The Israelis) know that whoever gets in next year will be in a much stronger position to lay down the law than is the case for a president in an election year."

Republicans are trying to capitalize on Obama's discomfort, with leading White House candidate Mitt Romney accusing him of "appeasement" and using the Iran showdown to try to dent Obama's foreign policy record.