Britain's foreign intelligence chief believes his agents prevented Iran from acquiring nuclear weapons but that the pariah state will become armed within two years, the Daily Telegraph reported on Friday.
In a rare public speech, MI6 boss John Sawyers told a meeting of around 100 senior civil servants in London that British agents had foiled Iran's attempts to produce a nuclear weapon as long as four years ago, according to the Telegraph.
"You'd have Iran as a nuclear weapons state in 2008 rather than still being two years away in 2012," the report quoted Sawyers as saying last week.
When Iran does finally acquire nuclear status, the intelligence chief warned that Israel and the United States would face huge dangers.
"I think it will be very tough for any Prime Minister of Israel or President of the United States to accept a nuclear-armed Iran," he suggested.
The US unleashed a fresh wave of sanctions against Iran on Thursday, ratcheting up pressure to convince Tehran to take seriously concerns about its suspected nuclear weapons programme.
The actions impose additional sanctions on Iran's nuclear and ballistic missile proliferation networks and identify Iranian "front" companies and banks to assist in compliance, the Treasury Department said.
"The Treasury and State Department actions target more than 50 entities tied to Iran's procurement, petroleum, and shipping networks," the Treasury said.
Iran has been subject to severe international economic sanctions over its controversial nuclear programme, which western powers believe masks an atomic weapons drive despite repeated denials by Tehran.