* Rubio says Iran is not serious about talks to end the war

* Three Saudi crude tankers for China and India turned back

in the Red Sea on Tuesday

* Trump said 18 US service members have been killed so far

in the war

* An Iranian health ministry official said recent US strikes

on Iran killed 50 civilians, wounded 500

DUBAI/MANILA, July 22 (Reuters) - U.S. 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 U.S.

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.

A senior Iranian official told Reuters on Monday that Tehran

had received a proposal from mediators for a 10-day ceasefire in

efforts to salvage the interim ceasefire agreement signed by the

U.S. and Iran in June, which replaced an earlier April

ceasefire.

In another sign that diplomacy remains alive, Iran's

Interior Minister Eskandar Momeni has visited mediator Pakistan

and asked Islamabad to continue its efforts.

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 U.S. 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 U.S. 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 ( AMZN )

in Bahrain, where the U.S. tech company operates a

regional data centre. Amazon ( AMZN ) did not comment and Reuters could

not verify the report.

U.S. President Donald Trump confirmed that 18 U.S. service

members had been killed so far in the war, including four in

Iranian attacks on U.S. 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 U.S. gasoline

back over $4 a gallon.

"GATE OF TEARS"

In a letter to shippers, the Houthis on Tuesday threatened

to attack any ships that load or discharge Saudi oil.

Trump said the Houthis had not yet shut the Bab el-Mandeb,

the "Gate of Tears" strait leading into the Red Sea, and

threatened to act against them if they did.

"So far it hasn't happened," Trump said. "If something like

that happens, we take care of it."

Three oil tankers loaded with Saudi crude for China and

India made U-turns in the Red Sea on Tuesday, heading towards

the Suez Canal rather than braving the Yemeni coast at the sea's

mouth.

Throughout the war, Saudi Arabia partially escaped the shipping

disruption by piping oil to Yanbu on the Red Sea instead. But a

full closure of that alternative route by the Houthis could

reduce global oil supply as it would leave most Saudi oil

exports trapped.

On Tuesday, Trump renewed his threats to again attack Iran's

nuclear facilities at Natanz "pretty soon", which he said in

June 2025 had been "totally obliterated" after the U.S. military

bombed the facility, buried in a mountain range, that month.

Iran promised it would retaliate.

Fifty civilians have been killed and 500 wounded in the

recent U.S. strikes on Iran, a health ministry official said.