Ben Wallace, UK defence secretary

Britain may have to fight future conflicts without the help of the US as its key ally, Defence Secretary Ben Wallace has warned.

Mr Wallace worries that the increasing isolationist policies of US President Donald Trump mean that the UK may need to rethink the assumptions that have underpinned its defence planning for the last 10 years.

The warning comes as Prime Minister Boris Johnson gets ready to lead the “deepest review” of Britain’s security, defence and foreign policy since the Cold War.

Speaking in The Sunday Times, the defence secretary said that the thought of the US stepping back from its international role “keeps me awake at night”.

He added: “I worry if the United States withdraws from its leadership around the world.

“That would be bad for the world and bad for us. We plan for the worst and hope for the best.”

Mr Wallace wants the UK to use the upcoming defence review to look into new capabilities that means it is less dependent on the US when it comes to future conflicts, saying: “Over the last year we’ve had the US pull out from Syria, the statement by Donald Trump on Iraq where he said NATO should take over and do more in the Middle East.

“The assumptions of 2010 that we were always going to be part of a US coalition is really just not where we are going to be.

“We are very dependent on American air cover and American intelligence, surveillance and reconnaissance assets. We need to diversify our assets.”

Mr Wallace also called for the armed forces to have a more modern approach, and said that any changes made in the upcoming review will need to “reflect the 21st century”, suggesting that this could mean infantry are replaced with “1,000 hackers” or better trained specialists, to help deal with modern threats.

He said: “How we deliver defence cannot be dominated by sentimentality. We really have to embrace new technology.”