British intelligence officials fear Vladimir Putin is preparing for a direct confrontation with Nato within months, believing the Kremlin sees a window of opportunity to test Western resolve.
Security sources believe the Russian President intends to probe Andy Burnham's fledgling Government following his succession of Sir Keir Starmer as Prime Minister, according to the Mail.
Moscow is said to believe that Donald Trump's growing focus on Iran has created an opportunity to increase pressure on the Western alliance.
One intelligence source told the Mail: "There's now a strong belief Putin is preparing some sort of direct confrontation with Nato at some point over the next couple of months."
The insider said the Kremlin believes Mr Trump's attention is increasingly consumed by the conflict with Iran while divisions within Ukraine's leadership have weakened Kyiv's position.
"There's a feeling that if he can't somehow change the momentum on the battlefield, the war will be lost," they added.
Intelligence officials also believe Mr Burnham's arrival in Downing Street could encourage the Kremlin to test Britain's resolve.
"He'll want to try and test Burnham, and see if he can exploit any divisions between the old and new administrations," the source said.
Moscow is said to believe that Donald Trump's growing focus on Iran has created an opportunity to increase pressure on the West
| GETTYThe warning comes after Russia's so-called shadow fleet was diverted away from the English Channel following last month's boarding of a sanctions-busting tanker by Royal Marine Commandos.
The vessels are now believed to be sailing north of the Shetland Islands, forcing the Royal Navy to expand its surveillance operations in the Atlantic.
A Russian frigate carried out live-fire artillery drills just 46 miles off the coast of Plymouth on the day Mr Burnham became Prime Minister.
The intelligence warning comes as Britain also faces growing threats from Iran after Tehran declared UK military bases "legitimate targets" for supporting American military operations.
RUSSIA - READ THE LATEST:
Intelligence officials also believe Mr Burnham's arrival in Downing Street could encourage the Kremlin to test Britain's resolve
| GETTYRAF Fairford, which has hosted US aircraft during the conflict, is now among the sites receiving enhanced protection from Britain's intelligence services.
Tim Ripley, editor of Defence Eye, said: "America's top commander in the Middle East, Admiral Brad Cooper, has confirmed that the Iranians have a type of missile with the range potentially to hit London."
Defence Secretary Wes Streeting insisted Russia should be left in no doubt about Britain's resolve.
He said: "Russia should be in no doubt about the resolve of this Government and this Prime Minister to stand against Russian aggression, not just in Ukraine, but also any aggression against the UK and our allies."
A Russian frigate carried out live-fire artillery drills just 46 miles off the coast of Plymouth
| GETTYIn recent days, Mr Streeting has reached out to Pentagon chief Pete Hegseth in a bid to repair transatlantic ties and coordinate a response to Iran's blockade of the Strait of Hormuz.
The two defence chiefs are said to have held talks this week, with Mr Streeting proposing a major London summit bringing together Nato allies, defence ministers and senior military figures from up to 40 countries.
The proposed gathering would reunite European and American allies after recent meetings were held separately.
A Ministry of Defence spokesman said Britain "stands ready 24/7" to counter air and missile threats.