French president Emmanuel Macron, the summit's host, invited Iranian foreign minister Mohammad Javad Zarif to talks on the sidelines to improve relations and said he hoped the U.S. and Iran could meet soon.
Tensions between Washington and Tehran have heightened since the USA pulled out of the 2015 Iranian nuclear deal past year.
Trump said Monday he was ready to meet Iran's President Hassan Rouhani within weeks, in a potential breakthrough reached during a G7 summit in the French seaside resort of Biarritz.
While some countries such as Australia and the U.K. have announced they will take part in the coalition, Japan has remained ambiguous on the matter, caught between its alliance with the United States and traditionally friendly ties with Iran.
"The White House was blindsided by the arrival of the Iranian foreign minister at the G7 summit", reported NBC News, citing three USA officials as its source.
"We support and welcome any diplomatic efforts to find the way out of the crisis, deescalate the situation in the region and preserve the JCPOA", the spokesperson said, referring to the acronym of the 2015 Iran nuclear deal that the European Union still supports.
On Sunday night, Zarif tweeted that he had met with Macron "on the sidelines" of the G7 summit and held "extensive talks" with a couple of French cabinet ministers, which was followed by a "joint briefing for UK/Germany".
"We are not seeking conflict with Iran", Defense Secretary Mark Esper told reporters at the Pentagon on Wednesday. "He doesn't want them to get the money from conventional means because he wants to maintain his policy of maximum pressure", Bandow said.
At the time, Trump said the terms of the deal were not strict enough to prevent Iran from developing nuclear weapons and that it was violating the "spirit" of the accord by financing extremist terror in the region - accusations Tehran has rejected.
The cyber conflict is part of the wider conflict between the USA and Iran that has stayed out of the public eye unlike their openly hostile exchanged regarding attacks in the Persian Gulf earlier this year which the US immediately blamed on Iran and Iran denied.
"I think they are going to change, I really do". Esper championed a US -led maritime security coalition known as Operation Sentinel, charged with patrolling the Persian Gulf.
Washington's call followed a series of attacks on worldwide merchant vessels, which the United States has blamed on Iran, and the Iranian seizure of a British oil tanker.
Zarif said the British tanker had violated Iran's sea laws and will need to go through the court system.