A defiant Iran vowed on Saturday to press ahead with its missile programme and condemned new US sanctions, as tensions rise after the West hardened its tone against the Islamic republic.
In the latest incident on the ground, Iran's Revolutionary Guards said the US Navy had approached their patrol vessels in the Gulf and fired flares.
"At 4 pm (1130 GMT) on Friday, the supercarrier USS Nimitz and its accompanying warship, while being monitored by the Guards' frigates, flew a helicopter near the Resalat oil and gas platform and approached the force's ships," the paramilitary force said.
"The Americans in a provocative and unprofessional move, sent a warning message to the frigates and fired flares," it said. The Guards "ignored the unconventional move by the US ships and continued their mission."
Three days earlier, a US Navy patrol ship fired warning shots at a Guards boat in the Gulf as it closed in on the American vessel, according to US officials.
The Guards denied approaching the US ship in Tuesday's incident and said it was the American vessel that had been at fault.
There have been a string of close encounters between US ships and Iranian vessels in the Gulf in recent months.
On the political battlefield, Iranian foreign ministry spokesman Bahram Ghasemi told state broadcaster IRIB that Tehran condemned new US sanctions against its missile programme, which President Donald Trump is set to sign into law, and vowed to press on.
"We will continue with full power our missile programme," he said. "We consider the action by the US as hostile, reprehensible and unacceptable, and it's ultimately an effort to weaken the nuclear deal."
Ghasemi was referring to a 2015 agreement between Iran and US-led world powers that lifted some sanctions on Tehran in return for curbs on the country's nuclear programme.
"The military and missile fields... are our domestic policies and others have no right to intervene or comment on them," the spokesman said.
The sanctions bill, which also targets Russia and North Korea, was passed by the US Senate on Thursday, two days after being approved by the House of Representatives.
Separately on Friday, Washington imposed new sanctions targeting Iran's missile programme, one day after Tehran tested a satellite-launch rocket.
Iranian state television broadcast footage of the takeoff from the Imam Khomeini space centre in Semnan province in the east of the country.
The launch vehicle was capable of propelling a satellite weighing 550 pounds (250 kilogrammes) into orbit at an altitude of 300 miles (500 kilometres), it said.
Western governments suspect Iran of trying to develop the technology for longer-range missiles with conventional or nuclear payloads, a charge denied by Tehran, which insists its space programme has purely peaceful aims.
In a joint statement, Britain, France, Germany and the US condemned Tehran's "provocative" and "destabilising" action, saying the test was in violation of UN Security Council Resolution 2231 that endorsed the nuclear deal.
"We call on Iran not to conduct any further ballistic missile launches and related activities," they said.
Resolution 2231 called on Iran not to test ballistic missiles capable of carrying a nuclear warhead and an arms embargo has remained in place.
The United States has had no diplomatic ties with the Iran since 1980, and Trump has halted the direct contacts initiated by his predecessor Barack Obama.
Tensions have mounted between Washington and Tehran since Trump took office six months ago vowing to be the best friend of Israel.
At UN headquarters in New York on Friday, US envoy Nikki Haley expressed mistrust of Iran.
"Iran's widespread support for terrorists tells us we can't trust them. Iran's breaking its obligation on missile testing tells us we can't trust them. Yesterday's launch proves that yet again," she said.
Despite his electoral promise to tear apart what he once called "the worst deal ever", Trump has so far respected the nuclear agreement.
The joint US-European statement said that Iran's latest test features technology related to "ballistic missiles designed to be capable of delivering nuclear weapons".
Iran insists it has "proven its compliance with the nuclear deal" as repeatedly confirmed by the International Atomic Energy Agency.
"Iran does not recognise any limits to its scientific and technological progress and will not wait for the approval or permission of any country regarding the activities of its scientists and experts," the foreign ministry spokesman said.