The White House on Monday denied an Israeli newspaper report that accused Washington of secretly negotiating with Tehran to keep the United States out of a future Israel-Iran war.
The Jewish state also played down the front-page report in its biggest-selling daily, Yedioth Ahronoth, which followed unusually public disagreement between the allies about how to tackle Iran's controversial nuclear program.
"It's incorrect, completely incorrect," White House spokesman Jay Carney told Reuters while accompanying President Barack Obama on a campaign trip in Ohio. "The report is false and we don't talk about hypotheticals."
Without naming its sources, Yedioth said Washington had approached Tehran through two unidentified European countries to convey the message that the United States would not be dragged into fighting if Israel carried out threats to attack Iran.
Yedioth said the United States told Iran it should in return refrain from retaliating against U.S. interests, including its military in the Gulf.
In Jerusalem, an Israeli official, who asked not to be identified, described the report as illogical.
"It doesn't make sense," the official said. "There would be no need to make such a promise to the Iranians because they realize the last thing they need is to attack U.S. targets and draw massive U.S. bombing raids."
In appearances on Sunday and Monday, Israeli Prime Minister Benjamin Netanyahu urged world powers to set a "clear red line" for Tehran's atomic program that would convince Iran they were determined to prevent it from obtaining nuclear arms. Such remarks have been portrayed in Israel as criticism of Obama.
Obama, who seeks re-election in November, is fighting accusations from his Republican challenger, Mitt Romney, that he is lax in support for Israel.
The Obama administration says it is strongly committed to Israel's security and to preventing Iran from obtaining a nuclear weapon. Iran says its nuclear program is entirely peaceful and has vowed far-ranging reprisals if attacked.
The United States and Israel both accuse Iran of secretly seeking the means to make nuclear arms and say they reserve the right to take military action to prevent Iran from getting them.
However, the Obama administration has repeatedly made clear in public that it thinks diplomacy and tough new sanctions have not yet run their course, even as Israeli officials say the window for effective military action is rapidly closing.
Israeli Deputy Prime Minister Dan Meridor said he still believed Obama's assurances that Washington was prepared to use force if needed to prevent Iran from developing a bomb.
"I don't know what kind of messages Yedioth Ahronoth heard," Meridor said. "But I think the Iranians understand ... that if they cross a line towards a bomb, they could encounter very strong resistance, including all the options that are on the table - as the American president has said."
Obama has had frosty relations with the right-wing Netanyahu, who is due to visit the United States this month.
The November 6 presidential election is seen hinging mostly on the U.S. economy with foreign policy taking a back seat. But support for Israel is an important issue for many U.S. voters, including evangelical Christians as well as Jews who could prove critical in battleground states like Florida and Pennsylvania.
Obama wants to shore up his advantage among Jewish voters. He received 78 percent of the Jewish vote in the 2008 election, but a nationwide Gallup poll in June showed him down to 64 percent backing versus Romney's 29 percent.
Administration officials have also made clear they regard the prospect of an Israeli attack on Iran with alarm.
General Martin Dempsey, chairman of the Joint Chiefs of Staff, was quoted in Britain's Guardian newspaper as saying of a prospective Israeli attack on Iran: "I don't want to be complicit if they choose to do it."
The Obama administration and the European Union imposed harsh new sanctions on Iran in July. U.S. officials say they hope that this will persuade Iran to curb its nuclear projects.
Of Dempsey's comments, Meridor said: "I'm sorry we've reached the situation where Dempsey said what he said, but this campaign (against Iran) is continuing and it must be conducted very wisely."
Netanyahu's cabinet is divided over the wisdom of attacking Iran, and Israeli officials have dropped heavy hints of a retreat on their strategy, under which Netanyahu would shelve threats of an attack now in return for a stronger public pledge from Obama on conditions that would provoke U.S. action in the future.
"The greater the resolve and the clearer the red line, the less likely we'll have conflict," Netanyahu said on Monday.