By Adam Brookes BBC Pentagon correspondent

US-led forces in Iraq rely on the Hercules for safe transport

The US Air Force has grounded 30 of its C-130 transport aircraft because of what it called severe cracking in parts of the wing structure.

Another 60 C-130 aircraft have been placed on what the air force calls restricted flight status.

The move comes less than two weeks after a British C-130 Hercules crashed in Iraq, but no UK planes are affected.

The US Air Force said it had been monitoring cracks in parts of the wing structure on its C-130s since 2001.

This week, its inspectors decided the problem was serious enough to ground 30 of the aircraft.

The C-130, better known in Britain as the Hercules, is a four-engine transport plane widely used by western armies and air forces.

The version of the aircraft grounded by the US Air Force is the C-130E, which is similar but not identical to the British C-130K, one of which crashed in Iraq at the end of January, killing 10 servicemen.

A Ministry of Defence spokesman in London said no RAF Hercules aircraft had been grounded.

He said that the British Hercules which crashed in Iraq would have had a different wing structure from that on the American version.

A US military spokesman said the decision to ground the aircraft was taken on the basis of the Air Force's own safety analysis.