Much of Israel's military equipment is supplied by the US

The GBU-28 is a 2,000-kg conventional weapon with a powerful warhead that can burrow through six metres (20 feet) of concrete or 30 metres of earth.

The sale has gone ahead despite concern that Israel might use the weapon for a unilateral attack against Iran.

Congress has 30 days to reject planned foreign military sales, but correspondents say it rarely does so.

Israel - assumed to be the Middle East's only nuclear-armed state - says it is not planning a military strike against the Islamic republic.

However, the bombs are to be fitted on its F-15 fighter jets, which would put Iran within range.

Some analysts say the deal may be intended by Washington to back up with a bit of military muscle European diplomatic efforts to avert the prospect of a nuclear-armed Iran.

Talks between the Europeans and Iran are deadlocked over Tehran's refusal to give up uranium enrichment which could be used for arms production.

The US has accused Iran of using its civilian nuclear programme as a cover to develop nuclear weapons, a charge Tehran denies.