US President Donald Trump and French President Emmanuel Macron have pledged to seek stronger measures to contain Iran, but Trump refrained from committing to a 2015 nuclear deal.
He also threatened Tehran with retaliation if it restarted its nuclear program.
At a news conference with Macron on Tuesday, the US president kept up his blistering rhetoric against the nuclear accord between Iran and world powers that he says does not address Tehran's rising influence in the Middle East or its ballistic missile program.
He called it insane, terrible and ridiculous.
"This is a deal with decayed foundations," Trump said. "It's a bad deal. It's falling down."
With a May 12 deadline looming for Trump to decide on restoring US economic sanctions on Tehran, Macron said he spoke to Trump about a "new deal" in which the US and Europe would tackle the outstanding concerns about Iran beyond its nuclear program.
Macron is using a three-day state visit to the US as a high-stakes bid to salvage the Iran nuclear deal, which many in the West see as the best hope of preventing Iran from getting a nuclear bomb and heading off a nuclear arms race in the Middle East.
Under Macron's proposal, the US and Europe would agree to block any Iranian nuclear activity until 2025 and beyond, address Iran's ballistic missile program and generate conditions for a political solution to contain Iran in Yemen, Syria, Iraq and Lebanon.
It was unclear whether Macron made substantial progress in his efforts to prevent Trump from pulling out of the 2015 deal, and Trump stressed there would be repercussions should Iran restart its nuclear program.
"If Iran threatens us in any way, they will pay a price like few countries have ever paid," Trump said.
But Trump said: "We will have a great shot at doing a much bigger, 'maybe deal, maybe not' deal."
It was unclear what a new deal would mean for the fate of the 2015 accord and whether other countries that signed it, such as China and Russia, would agree to new measures against Iran.
German Chancellor Angela Merkel was expected to also make a case for the accord during a lower-key visit to the White House on Friday.
Iran has said it will ramp up its nuclear program if the deal collapses and a senior Iranian official said Tehran might quit a treaty designed to stop the spread of nuclear weapons if Trump scrapped the agreement.
Macron hopes to leverage his friendship with Trump into progress on not only Iran but exempting Europe from steel tariffs, and protecting the 2016 Paris climate accord.
Their talks also covered the US presence in Syria weeks after the United States, France and Britain launched air strikes in retaliation for a chemical weapons attack blamed on Syrian President Bashar al-Assad.
Trump wants to withdraw US forces from Syria, believing Islamic State militants are largely defeated, but Macron and other allies argue they should stay to ensure militants do not resurface and to block Iran from strengthening its foothold.
