The UK could trigger tensions with Iran as it gears up for its ‘funeral of the century’ by ploughing ahead with plans to de-mine the Strait of Hormuz.

Despite an apparent call from Tehran not to carry out any military operations during the official mourning period for its former leader Ayatollah Ali Khamenei, the UK and France are planning to join Oman in the operation in the crucial shipping channel.

In a joint statement with French President Emmanuel Macron, Sir Keir Starmer said British forces have agreed to work with Oman ‘to ensure that its sovereign territorial waters are safe for navigation’.

The announcement came a week ahead of a key NATO summit in Turkey with the two countries apparently keen to signal their solidarity with the US following past American criticism the allies’ response to the US Israeli war on Iran has been lacklustre at best.

Meanwhile up to 20 million people are expected to pour into Iran for a showpiece funeral for the former 86-year-old Iranian leader who was killed in air strikes more than four months ago at the start of the conflict.

In what is being seen as a major Iranian propaganda exercise, several days of public mourning have been announced to mark the funeral which has finally been enabled by the fragile ceasefire agreement.

But it is understood that any operations in the strait, control over which Iran has increasingly used as a vital pawn in peace negotiations, will be in direct contradiction of a request from authorities in Tehran to cease any operations during the mourning period.

A Whitehall source said there was concern the UK and French operation could fracture the current period of calm.

Sir Keir Starmer said British forces have agreed to work with Oman ‘to ensure that its sovereign territorial waters are safe for navigation’ in the Strait of Hormuz 

French President Emmanuel Macron made the joint declaration with Britain as political insiders warned the de-mining operation could trigger tensions with Iran

It is understood that any operations in the strait will be in direct contradiction of a request from Tehran to cease such activities during the mourning period. Pictured: The Strait of Hormuz near the beach of Bandar Abbas, Iran

But the two leaders who reaffirmed their ‘shared commitment’ to ‘uphold global security, freedom of navigation and international law’ are said to be keen to show to a previously critical President Trump that they are prepared to ‘play their part’, the source told today’s Times.

Ahead of the funeral, the former Ayatollah’s body is lying in state in Tehran where officials have been paying their respects.

With Western leaders absent from the funeral, representatives from Iraq, Armenia, Turkey and several Gulf states including those bombed by Iran at the start of the war – Saudi Arabia, Oman and Qatar – will attend the official funeral ceremony today.

In a separate development, the outgoing PM warned his likely successor Andy Burnham would have to spend just as much time on international relations as he had done during his premiership.

He told the BBC: ‘There’s often this discussion — what’s the right balance between dealing with international affairs and dealing with domestic affairs?

‘They’re one and the same thing. Whoever’s my successor is going to face the same global conflict. We keep saying, and it’s true, we’re in a more dangerous and volatile world than we’ve been in for probably most of my lifetime.

‘That’s not just a phrase, that’s reality. That’s not going to change. And the domestic challenges aren’t going to change.’

And with his long awaited defence spending plan finally announced this week to much derision, he could also face a roasting from Trump in Turkey over the UK’s commitment to defence.

The US President, celebrating Independence Day this weekend, has already lashed out on his Truth Social account at NATO allies’ defence spending plans, comparing the US’s vast $999 billion NATO commitment to their planned contributions.

‘Ridiculous for the USA to continue along this one sided path when the relationship is not reciprocal. They were not for us!!!’ he said.

Meanwhile a senior UK military source said that £15 billion earmarked for defence by Starmer meant that ‘yet again we have failed to align ambition with resources’.