RUSSIAN leader Vladimir Putin is likely to have known about a plot to assassinate former spy Alexander Litvinenko in London, a US diplomat has claimed.

Senior US ambassador Daniel Fried made the allegation in talks with the French, a month after the Russian dissident was killed by polonium-210 poisoning in November 2006.

Mr Litvinenko defected to the UK in 2000 and set up home in Muswell Hill. He died an agonising death in hospital after being exposed to the isotope during a meeting at a central London hotel.

The diplomatic cable, released to the public for the first time by website Wikileaks, said Mr Fried was doubtful “rogue elements” in the Russian secret service could carry out an operation like this without approval.

The cable read: “Fried, noting Putin's attention to detail, questioned whether rogue security elements could operate, in the UK no less, without Putin's knowledge.

“Describing the current atmosphere as strange, he described the Russians as increasingly self-confident, to the point of arrogance.”

He was in talks with Maurice Gourdault-Montagne, senior adviser to French President at the time Jacques Chirac.

Mr Gourdault-Montagne, according to the cable, doubted Mr Fried's theory. It said: “He wondered aloud who might have given the order, but speculated the murder probably involved a settling of accounts between services rather than occurring under direct order from the Kremlin.”

The leaked cables are sending shockwaves through the diplomatic community, as thousands of secret US messages are gradually released publicly, causing embarrassment for American diplomats.

Other cables on the Litvinenko case discuss theories and rumours about his death, from blaming it on suicide to suggesting the hit was carried out to undermine President Putin.

Former KGB officer Andrei Lugovoi is the prime suspect in the murder case, but Russian officials have refused to extradite him to the UK to stand trial.

A cable from 2007 revealed the US believed in May 2007 it was “highly unlikely” Mr Lugovoi would be extradited, despite the damage this would do to Russia's international reputation.