ABOARD THE USS GEORGE WASHINGTON — The U.S. Navy on Tuesday offered Australia any help it wanted to retrieve four bombs mistakenly dropped inside the World Heritage-listed Great Barrier Reef marine park last week.

U.S. Navy Harrier 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.

The aircraft, which were not able to land safely carrying the bombs, were participating in Operation Talisman Saber, a joint U.S.-Australian military exercise involving nearly 30,000 personnel, mostly around northern Australia.

Vice Admiral Scott Swift, the commander of the U.S. 7th Fleet, said a decision on whether to leave the bombs or retrieve them was up to the Australian government.

"Once that determination has been made, we'll work closely with whoever is designated to remediate the problem. If that means removal of the weapons, I'd be happy to participate," Swift told media aboard an aircraft carrier, the U.S.S. George Washington, 200 km (125 miles) off the Australian coast.

The bombs were lying in 50 to 60 meters (160 ft to 200 ft) of water, posed little risk to the reef or shipping and could easily be picked up by Navy divers, a spokesman added.

Environmentalists have criticized 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, the United Nations says.

Swift and Australian Brigadier General David Coghlan said the site had been used for decades and the risks were manageable.

"We have a long history of good stewardship in that area and we have a solid environmental program," Coghlan said. "We look at the risk every year, every day."