The Australian Defence Force says four unarmed bombs dropped on the Great Barrier Reef by US planes pose "minimal risk".
The ADF confirmed that the two jets each dropped two bombs on the reef in an emergency during a joint training exercise near Rockhampton on Tuesday.
A spokesman told AAP the four bombs posed "minimal risk or threat to the public, the marine environment or civilian shipping in the reef area".
NBC News in the United States reported the two AV-8B Harrier jets intended to drop the bombs on a range on Townshend Island, but the range was not clear.
They attempted the drop the ordinance several times and began to run low on fuel, realising they could not land with the bombs.
"They chose to save the aircraft," a US official told NBC.
Each jet dropped two 225kg unexploded bombs in about 60 metres inside the marine park.
AAP reports a salvage operation is expected to recover the bombs.
The jets were part of training exercise Talisman Saber, involving 28,000 personnel from the ADF and US military.
The exercise began on Monday in locations along the Queensland coast and ends 5 August.