Britain's decision to engage directly with elements of Hezbollah is causing unease in the Obama Administration, which continues to regard the Lebanese-based militant group as a terrorist organisation.

A public row erupted between London and Washington after a media briefing this week with Jeffrey Feltman, the acting Assistant Secretary of State for Near Eastern Affairs. Mr Feltman, a Bush appointee who has stayed on temporarily as America's top diplomat for the region, is a former ambassador to Lebanon known for his strong anti-Hezbollah views.

After the briefing, a senior State Department official was quoted as saying the US wanted Britain to explain “the difference between the political, military and social wings of Hezbollah because we don't see a difference between the integrated leadership that they see”.

The Foreign and Commonwealth Office announced last week that it planned to take up “carefully selected” contacts within the political wing of Hezbollah, which is part of Lebanon's governing coalition. Its military wing is an internationally proscribed terrorist organisation.

The announcement followed two years of unofficial contacts, including visits by British parliamentarians led by the Conservative Michael Ancram to Beirut and Damascus.

Asked if Washington had been given warning of Britain's decision, the State Department official replied that “informed under a previous administration” would be a “more accurate description”.

Senior British officials strongly denied that the Obama Administration had been “blindsided”.

“We were in close contact with Washington throughout the process,” a senior Whitehall official said. “This should not have come as a shock to any official who might have been in the previous administration and is now in the current one.”

America blames Hezbollah for attacks in the 1980s, when its embassy in Beirut was hit twice by suicide bombers and 241 Marines were killed in a truck bombing of their barracks.

Times Recommends

• 'New York has lost its edge'
• Copenhagen will fail – and quite right too
• More than 17,000 new underwater species found