US President Donald Trump has been warned that the world is now already sliding into World War 3 thanks partly to his military operation in Iran.

Ray Dalio, an author and founder of one of the world’s largest hedge funds, issued the dire warning as he predicted that Russia and China could even become involved.

He said: “For today, that is most importantly that the US-Israel-Iran war is just part of a world war that we are in and that isn’t going to end anytime soon.”

On the conflict in Iran, Mr Dalio added that China and Russia appear to be “the relative economic and geopolitical winners from this war.”

Mr Dalio’s bleak prediction outlines 13 major characteristics of the ‘world war’, including direct military encounters between major powers, economic warfare, financial crises, the development of new war techologies, and markets being shut down.

He adds that “eventually, one side beats the other and gains indisputable control of the new order, which is designed by the winning side.”

Mr Dalio concluded: “As history has shown, the most reliable indicator of which country is likely to win is not which is most powerful; it is which can endure the most pain the longest.”

His comments come as the head of the UK’s armed forces confirmed that Britain is working on a plan to prepare for war.

Air Chief Marshal Sir Richard Knighton told Sky News: “I talked before Christmas of the need that when we think about renewing our water infrastructure or electricity or transport infrastructure, to think about the threat of action from an adversary that is above the threshold of war, not just a hybrid threat,” he said.

“And think about how we build in that resilience as we renew it, and that requires making some different choices and different priorities, and that work that the Cabinet Office is doing across the whole of Government is something that I really welcome.”