Rubio met British foreign minister David Lammy on Thursday and held separate calls with Australian Foreign Minister Penny Wong, French Foreign Minister Jean-Noel Barrot and Italian Foreign Minister Antonio Tajani to discuss the conflict.
The US State Department said Rubio and the foreign ministers agreed that "Iran can never develop or acquire a nuclear weapon."
Lammy said the same on X while adding that the situation in the Middle East "remained perilous" and a "window now exists within the next two weeks to achieve a diplomatic solution."
US President Donald Trump says he will decide in the next two weeks whether the US will get involved in the war, the White House said.
The foreign ministers of Britain, France, Germany and the European Union were due to meet Iran's foreign minister in Geneva on Friday to try to create a pathway back to diplomacy.
The ministers from the countries, known as the E3, spoke to Abbas Araqchi earlier this week.
In a rare call they pressed upon Araqchi the need to return to the negotiating table and avoid further escalation. At Iran's suggestion the two sides agreed to meet face-to-face.
Negotiations between Iran and the United States collapsed when Israel launched what it called Operation Rising Lion against Iran's nuclear facilities and ballistic capabilities on June 12.
"The Iranians can't sit down with the Americans whereas we can," said a European diplomat. "We will tell them to come back to the table to discuss the nuclear issue before the worst case scenario, while raising our concerns over its ballistic missiles, support to Russia and detention of our citizens."
The European powers, who were not part of Iran's nuclear negotiations with the United States, had grown increasingly frustrated by the US strategy in the talks. They deemed some of the demands unrealistic, while fearing the possibility of a weak initial political framework that would lead to open-ended negotiations.
Diplomats said it was vital to engage with Iran because once the war stopped, Iran's nuclear program would still remain unresolved given that it would be impossible to eradicate the know-how acquired, leaving it potentially able to clandestinely rebuild its program.
An Iranian official urged the E3 to use all available means to pressure Israel to halt its attacks on Iran.
"Iran remains committed to diplomacy as the only path to resolving disputes — but diplomacy is under attack," the official said.
Prior to Israel's strikes the E3 and US put forward a resolution that was approved by the Board of Governors of the International Atomic Energy Agency, a UN watchdog, which declared Iran in breach of its nuclear non-proliferation obligations.
As part of last week's IAEA resolution, European officials had said they could refer Iran to the United Nations Security Council later in the summer to add pressure on Iran if there was no progress in the nuclear talks.
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