US President Joe Biden on Friday advised Israel against striking Iran's oil facilities, saying he was trying to rally the world to avoid the escalating prospect of all-out war in the Middle East.
But his predecessor Donald Trump, currently campaigning for another term in power, went so far as to suggest Israel should "hit" the Islamic republic's nuclear sites.
Making a surprise first appearance in the White House briefing room, Biden said that Israel's Benjamin Netanyahu "should remember" US support for Israel when deciding on next steps.
"If I were in their shoes, I'd be thinking about other alternatives than striking oil fields," Biden told reporters, when asked about his comments a day earlier that Washington was discussing the possibility of such strikes with its ally.
Biden added that the Israelis "have not concluded how they're, what they're going to do" in retaliation for a huge ballistic missile attack by Iran on Israel on Tuesday.
The price of oil had jumped after Biden's remarks on Thursday.
Any long-term rise could be damaging for US Vice President Kamala Harris as the Democrat confronts Republican Trump in a November 5 election where the cost of living is a major issue.
Meanwhile Trump, campaigning in North Carolina, offered a far more provocative view of what he thinks a response to Iran should be, referencing a question posed to Biden this week about the possibility of Israel targeting Iran's nuclear program.
"They asked him, 'what do you think about Iran, would you hit Iran?' And he goes, 'As long as they don't hit the nuclear stuff.' That's the thing you want to hit, right?" Trump told a town hall style event in Fayetteville, near a major US military base.
Biden "got that one wrong," Trump said.
"When they asked him that question, the answer should have been, hit the nuclear first, and worry about the rest later," Trump added.
Trump has spoken little about the recent escalation in tensions in the Middle East. But he issued a scathing statement this week, holding Biden and Harris responsible for the crisis.
Biden's appearance at the famed briefing room podium was not announced in advance, taking reporters by surprise.
It comes at a tense time as he prepares to leave office with the ongoing escalation in the Middle East triggered by Israel's war in Gaza and invasion of south Lebanon boiling over, and political criticism at home over his handling of a recent hurricane that struck the US southeast.
Biden said he was doing his best to avoid a full-scale conflagration in the Middle East, where Israel has killed close to 42,000 Palestinians and nearly 2,000 people in Lebanon since October 7 last year.
"The main thing we can do is try to rally the rest of the world and our allies into participating to tamp this down," he told reporters.
"But when you have (Iranian) proxies as irrational as Hezbollah and the Houthis (of Yemen), it's a hard thing to determine."
Biden however had tough words for Netanyahu, with whom he has had rocky relations as he seeks to manage Israel's military campaign in Gaza.
The Israeli premier has repeatedly ignored Biden's calls for restraint on Lebanon, and on Israel's war in Gaza.
Despite Biden's harsher words for the Israeli Prime Minister, the US President's administration has maintained strong financial and military support for Israel throughout its war in Gaza, providing billions of dollar in arms support.
Kamala Harris, Biden's VP, has repeatedly rejected calls for a US arms embargo on Israel.
Biden deflected a question on whether he believed Netanyahu was hanging back on signing a Middle East peace deal in a bid to influence the US presidential election.
"No administration has helped Israel more than I have. None, none, none. And I think Bibi should remember that," Biden said.
"And whether he's trying to influence the election, I don't know, but I'm not counting on that."
Biden said he had still not spoken to Netanyahu since the Iranian attack, which involved some 200 missiles, but added their teams were in "constant contact."
"They're not going to make a decision immediately, and so we're going to wait to see when they want to talk," the US leader added.
Iran said its attack was in retaliation for the killing of Hezbollah leader Hassan Nasrallah, and Hamas leader Ismail Haniyeh, who was killed in Tehran in attacks blamed on Israel.