The US Navy in the Pacific has a problem.

Not only has it lost two of its most advanced air defence destroyers to avoidable collisions at a time of intense regional tensions, there are reports its crews are on the brink of exhaustion - and revolt.

The Navy Times has revealed a catastrophic collapse of morale aboard the key guided missile cruiser USS Shiloh - one of only a handful of ships capable of engaging North Korea's ballistic missiles.

"If we went to war I felt like we would have been killed easily and there are (people) on board who wanted it to happen so we could just get it over with," one sailor wrote.


"It's only a matter of time before something horrible happens," another predicts in an anonymous survey of the Japan-based USS Shiloh's mission preparedness.

But these are just a few words among a flurry of expressions of discontent:

"Our sailors do not trust the CO."

The ship's a "floating prison".

"I just pray we never have to shoot down a missile from North Korea ... because then our ineffectiveness will really show."

Pushed to the limit

Depression. Suicidal thoughts. Exhaustion. Despair.

The cause?

Micromanagement. Command dysfunction. Excessive punishments.

Some even say they had been confined to the 'brig' on bread and water rations for simple on-the-job mistakes.

The responses are being seen as a warning that the stressed US 7th Fleet may not be up to the task of deterring North Korea, China and Russia amid a multitude of regional stand-offs.

"Members, especially leaders, are so worn out, beat down, and overworked, that they are almost incapable of being effective," one sailor wrote.

Such comments are reportedly common among the returned surveys, each of which contains hundreds of pages of questions.

Key among them are concerns their ageing warship has been repeatedly rushed back to sea without vital repairs being completed.

"It feels like a race to see which will break down first, the ship or its crew," one survey response warns.

The USS Shiloh sounded a "man overboard" alarm earlier this year, initiating a fruitless 50-hour search and rescue operation. The missing man was later found hiding aboard the ship.

Navy officials have refused to discuss the survey, but say the USS Shiloh's commanding officer - who was rotated away from the ship under standard practice on August 30 - was having his conduct investigated.

It comes on the back of a growing number of reports highlighting overworked and under-trained US navy crews in the Pacific making simple - but sometimes fatal - mistakes.

'Loss of confidence'

The US navy yesterday sacked two top commanders from a different warship that was involved in a deadly collision with a tanker off Singapore, citing a "loss of confidence" in the officers.

On August 21, the guided-missile destroyer USS John S. McCain smashed into a tanker as the warship headed to Singapore, tearing a huge hole in the hull.

The collision killed 10 sailors and injured five others.

That incident came after another destroyer, the USS Fitzgerald, collided with a Philippine-flagged cargo ship off Japan in June, leaving seven sailors dead.

Commanding officer Alfredo J. Sanchez and executive officer Jessie L. Sanchez of the USS John S. McCain "were relieved of their duties", the Pacific-based US Seventh Fleet said in a statement.

"Both were relieved due to a loss of confidence," it said.

Two non-deadly incidents also occurred this year - in January, the guided missile cruiser USS Antietam ran aground near its base in Japan and in May, the guided missile cruiser USS Lake Champlain collided with a South Korean fishing vessel.

Following the USS McCain incident, the Navy sacked the commander of the Seventh Fleet, and several other officers and enlisted sailors have been relieved of duty or reprimanded.

But the pressures on the 7th Fleet continue to mount.

Multitude of missions

A US Navy destroyer has sailed near islands claimed by China in the South China Sea, even as President Donald Trump's administration seeks Chinese co-operation in reining in North Korea's missile and nuclear programs.

The operation yesterday was the latest attempt to counter what Washington sees as Beijing's efforts to limit freedom of navigation in the strategic waters. But it was not as provocative as previous ones carried out since Trump took office in January.

Three US officials, speaking on condition of anonymity, said the USS Chafee, a guided-missile destroyer, carried out normal manoeuvring operations that challenged "excessive maritime claims" near the Paracel Islands, among a string of islets, reefs and shoals over which China has territorial disputes with its neighbours.

China's claims in the South China Sea, through which about $US5 trillion ($9 trillion) in shipborne trade passes each year, are contested by Brunei, Malaysia, the Philippines, Taiwan and Vietnam.

Speaking in Beijing, Chinese Foreign Ministry spokeswoman Hua Chunying said China had lodged "stern representations" with the United States, and reiterated that the Paracels were Chinese territory.

"China immediately sent naval vessels and military jets to investigate and identify, as well as warn to the vessel and ask it to leave," she told a daily news briefing yesterday.

"China will continue to take resolute measures to protect Chinese sovereign territory and maritime interests. China urges the US to conscientiously respect China's sovereign territory and security interests, conscientiously respect the efforts regional countries have made to protect peace and stability in the South China Sea, and stop these wrong actions."

Unlike in August, when a US Navy destroyer came within 12 nautical miles (22km) of an artificial island built up by China in the South China Sea, officials said the destroyer on Tuesday sailed close to but not within that range of the islands.

Twelve nautical miles mark internationally recognised territorial limits. Sailing within that range is meant to show the United States does not recognise territorial claims.

The Pentagon did not comment directly on the operation, but said the United States carried out regular freedom-of-navigation operations and would continue to do so.