US Secretary of State Marco Rubio said on Wednesday the United States ​is still willing to negotiate an end to the Iran crisis, but Tehran is not serious about talks, as the widening conflict disrupted two of the world’s most critical ‌energy chokepoints.

Rubio made his comments in a meeting of Southeast Asian foreign ministers a day after three oil tankers carrying Saudi crude to Asia reversed course in the Red Sea, apparently in response to threats from Yemen’s Iran-aligned Houthis.

The Houthis, who control the coast at the mouth of the Red Sea, announced a naval blockade on Saudi Arabia on Monday, opening a potential new front in the war which has killed thousands of people across the Gulf since it began on February 28 with US and ​Israeli attacks on Iran.

With Iran already threatening shipping through the Strait of Hormuz leading out of the Gulf, the Red Sea has served as the main alternate route out for millions ​of barrels of Saudi oil per day.

Rubio said Washington was “always committed to diplomacy” but doubted whether Tehran was equally committed to negotiations.

“The problem we’re having right now is that they’re not serious about talks. ​If they’re serious, we’re serious. If they’re not, then we will do what’s necessary to protect our interests, and also the interests of our allies,” Rubio said in Manila.

He stressed that Iran could not be allowed to control the Strait of Hormuz, arguing it would create a dangerous precedent for the world, including Southeast Asian countries, many of which have territorial disputes in the South China Sea with China.

“If we create a precedent in the Middle East where a nation state can ​decide that they are going to control an international waterway, charge a toll, and if you don’t pay them, blow up your ships, we have created a very dangerous precedent, which will repeat itself in ​other parts of the world, including in this region,” Rubio said.

With no diplomatic breakthrough in sight, the US military bombed targets across Iran for an 11th straight night on Tuesday.

Tehran residents reported hearing explosions in the early hours ‌of Wednesday ⁠as Iran activated its air defences over the capital, Iran’s semi-official Fars news agency said.

Explosions were also reported in the southeastern coastal cities of Chabahar and Konarak, and two blasts were heard in Bushehr, home to Iran’s only nuclear power plant, Iran’s official IRNA news agency reported.

Earlier, Iran targeted US military sites in Bahrain, Kuwait and Jordan and a tanker was hit in the Strait of Hormuz.

Iran said it had struck infrastructure belonging to Amazon in Bahrain, where the US tech company operates a regional data centre.

Amazon did not comment, and Reuters could not verify the report.

US President Donald Trump confirmed that 18 US service members had been ​killed so far in the war, including four ​in Iranian attacks on US military bases in ⁠Jordan and Iraq over the last few days.

Oil prices rose further in Asian trade on Wednesday after climbing more than 2% on Tuesday following the Houthi threats, with Brent crude hovering above $91 a barrel and US gasoline back over $4 a gallon.