Iran said on Thursday that the Strait of Hormuz was an inviolable "red line", warning that if US President Donald Trump carried out his threat to attack Iran's infrastructure, it would strike infrastructure across the Gulf region.
The United States launched a fifth consecutive night of attacks on Wednesday and reimposed a naval blockade on Iranian ports, which Washington says is aimed at reopening the Strait of Hormuz, closed by Iran last Saturday after a fragile truce collapsed.
Following the first strikes on Wednesday night, Tehran's top negotiator, Mohammad Baqer Qalibaf, issued a statement saying: "We are in an essential and existential war with America."
Iranian army spokesman Brig Gen Mohammad Akraminia said on Thursday that the Strait of Hormuz, through which about one-fifth of global oil and gas shipments passed before the war, was a "red line" for Iran, over which it maintained firm control.
"The Americans thought that by attacking some of our bases on the southern coasts of the country, they could take control of this strategic strait," Akraminia said.
"However, the Islamic Republic of Iran has the ability to exert control over the Strait of Hormuz from every single point of its territory, and this matter is never dependent on coasts and islands."
Three US officials told Reuters that the US strikes aimed at reopening the strait were also targeting Iranian military capabilities that Washington would want to destroy before carrying out more complex operations.
Iran's army earlier said of the strait: "We will undoubtedly resist until the end and will neutralise American interventions in the region."
An Iranian military spokesperson said the only way to reopen the Strait of Hormuz was for the United States to comply with the 14-point memorandum of understanding signed by the two sides in June, and to implement "Iranian regulations" governing shipping through the strait.
Trump warned on Tuesday that he would target Iranian power plants and bridges next week unless Tehran resumed negotiations.
Akraminia said that if Trump carried out the threat, Iran's armed forces would strike "all remaining infrastructure" across the region, and that the response would be more severe, wider in scope and more destructive than previous attacks.
Iran also said on Thursday that it had targeted US bases in Kuwait and Jordan, warning neighbouring countries that allowing the United States to launch attacks against Iran from their territory would not go unanswered.
"Our neighbours should know that providing a base to the Americans and allowing them to fire on Iranian soil is unacceptable and will not go unanswered," Iran's army said in a statement.
By early Thursday in the Middle East, sirens had sounded in Bahrain, while Kuwait said it was responding to "hostile drone threats".
Iran's army said it had targeted Jordan's Al Azraq Air Base with ballistic missiles, while Iran's Revolutionary Guards said they had destroyed the satellite communications centre and early warning radar at Kuwait's Ali Al Salem Air Base, as well as a US military pier in the Al Shuaiba area.
Bahrain's Defence Ministry said the country's air defence systems had intercepted and destroyed a number of Iranian aerial attacks targeting the kingdom on Thursday.
The latest escalation, together with Iran's threats to cut off more regional energy exports and potentially strike infrastructure across the Gulf, has raised the spectre of a return to full-scale war in the region.
Analysts say Iran has signalled it may use its Houthi allies in Yemen to close the Bab el-Mandeb gateway to the Red Sea, opening a new front against Washington and placing a second of the world's most vital energy shipping routes at risk.
The war has killed thousands of people and displaced millions, mainly in Iran and Lebanon, where fighting resumed between Israel and the Iran-backed militant group Hezbollah.
The conflict has also intensified concerns over global energy supplies, with the Strait of Hormuz remaining one of the world's most critical maritime chokepoints. Around one-fifth of global oil and gas shipments passed through the waterway before the conflict, making any prolonged disruption a major risk to international markets.
Iran has repeatedly insisted that its actions are a response to what it describes as US aggression, while Washington says its military campaign is intended to restore freedom of navigation and prevent Tehran from threatening international shipping.
Officials on both sides have continued to exchange warnings, raising fears that the conflict could spread further across the Middle East despite international calls for de-escalation.