BBC News Online examines the key stages of the operation.

FBI agents posing as Muslim extremists claim to have approached Hemant Lakhani, an alleged British arms dealer, about buying a missile in St Petersburg, Russia.

1. Missile bought in St Petersburg, inert copy shipped to US 2. Dealer flies from London to New York 3. Missile arrives and is stored in Baltimore warehouse 4. Lakhani arrested in hotel in Newark 5. Two further suspects arrested in New York

It is claimed that a Russian arms factory then provided Mr Lakhani with a Russian-made shoulder-launched SA-18 Igla missile, in a move approved by the US.

But specialists had already rendered the missile inert and removed its explosive content before despatching it.

The arms dealer is said to have flown to New York on Sunday 10 August on a British Airways flight from London.

The weapon arrived from Russia on Tuesday afternoon at a port in Newark, New Jersey, with the full knowledge and co-operation of US officials.

The missile was stored at a warehouse in Baltimore, allegedly disguised as medical equipment.

Laying in wait

It is claimed that Mr Lakhani arrived in the US to complete the cash transaction of $85,000 (�50,000) with the men who had ordered the weapon.

But he was arrested late on Tuesday at a hotel in Newark, New Jersey after returning from collecting a crate, said to contain the missile, from the Baltimore warehouse.

Scotland Yard has revealed that it issued two warrants to search premises in the UK on Tuesday morning, in connection with possible links to the missile deal.

Two more men were arrested at a New York gem dealership on Fifth Avenue and charged with helping to finance the deal.

The trio are expected in court in New Jersey on Wednesday morning - at about 1400 GMT (1500 BST).

It has been reported the FBI officers who placed the order specified the weapon should be able to be used to attack an airliner.

FBI officials began to focus on the threat from shoulder-mounted missiles in November, when unknown assailants narrowly missed an Israeli charter flight taking off from Mombasa, Kenya.

In May, another missile missed a US military jet taking off from Prince Sultan Air Base in Saudi Arabia.