The US Navy will lead the effort to recover four unarmed bombs it was forced to drop last weekend in Australia's World Heritage-listed Great Barrier Reef marine park. 

The US Navy has issued a statement that the 7th Fleet would take the lead in recovering the bombs, coordinating with Australian authorities to ensure "the environment is protected with the greatest care".

"We are fully committed to redressing any potential adverse environmental impact in a timely manner," the navy said, adding it would announce more detailed plans as they were finalised.

Two US fighter jets were forced to drop the bombs, two inert and two carrying explosives but not armed, after civilian boats were spotted near their original target during a biennial joint exercise with the Australian Defence Force.

The bombs were lying in 50 to 60 metres of water, posed little risk to the reef or shipping and could be picked up by divers, according to the Navy.

Environmentalists have criticised holding such large-scale military exercises in sensitive areas such as the Great Barrier Reef, which is under threat from increased commercial shipping, climate change and an invasive starfish infestation.