By John Irish

KANANASKIS, Alberta (Reuters) -French President Emmanuel Macron on Tuesday underlined his differences with U.S. President Donald Trump over Iran, appearing to oppose tougher military action against Tehran that could lead to regime change and plunge Iran and the region into chaos.

Macron on Monday had suggested to reporters that Trump was leaving the G7 as part of efforts to secure a ceasefire between Israel and Iran.

He was firmly rebuffed Tuesday morning when Trump on X said Macron was mistaken and said his departure had nothing to do with securing a ceasefire.

Since Tuesday morning, Trump has upped the bellicose rhetoric demanding Iran's "unconditional surrender" and warning that U.S. patience was wearing thin as the Israel-Iran air war raged for a fifth day.

Israel has said it launched its operation to stop Iran from acquiring a nuclear weapon, something Tehran has repeatedly denied.

Macron said Trump appeared to have changed his opinion since he met G7 leaders in Canada on Monday where Macron claimed Trump had told them he was pushing for a ceasefire.

"We don't want Iran to get a nuclear weapon," Macron said. "But the biggest error would be to use military strikes to change the regime because it would then be chaos and our responsibility is to return discussions as quickly as possible to be able to set a course again on the nuclear and ballistic question."

Macron said Iran's nuclear program had to be once again be put under international supervision and its ballistic missile arsenal reduced, but he was categorically opposed to strikes on energy infrastructure, civilians and military action that could lead to regime change.

Israeli Defence Minister Israel Katz said Iran's Supreme Leader Ayatollah Ali Khamenei could face the same fate as Iraqi President Saddam Hussein, who was toppled in a U.S.-led invasion and hanged in 2006 after a trial.

"Does anyone think that what was done in Iraq in 2003 was a good idea? Does anyone think that what was done in Libya the next decade was a good idea? No!," Macron said.

"I'm also thinking of our friends in the region, in Iraq, Lebanon, and elsewhere. We must help them reduce everything that, indeed, threatens their security, but they need anything but chaos."

Macron's comments were also in stark contrast with German Chancellor Friedrich Merz, who said Israel was doing the "dirty work" for its Western allies, but could fall short without U.S. support.

Israel has severely hit Iran's nuclear program, but without U.S. firepower can likely not destroy Fordow, a plant dug deep into a mountain, where Iran has enriched uranium up to 60%, close to the 90% weapons grade.

"The Israeli army is obviously unable to accomplish that. It lacks the necessary weapons. But the Americans have them," said Merz in an interview with broadcaster ZDF.

In another interview he said the decision could be made soon depending on whether Iran was prepared to return to the negotiating table.

(Reporting by John Irish; Editing by Chris Reese and Alistair Bell)