President Donald Trump has named US Pacific Commander Admiral Harry Harris as his pick to serve as the American ambassador to Australia.

The naval officer has served in the military for 39 years and is in his seventh command assignment as head of the US Pacific Command, according to the White House.

During Harris' tenure as head of US forces in the Pacific, tensions over North Korea's missile and nuclear programs increased as President Donald Trump's administration and Pyongyang exchanged threats.

Harris, who was appointed by former President Barack Obama, favours diplomacy in countering North Korea's missile threat.

Harris is also known for his combative views on Beijing's South China Sea expansion and a strong supporter of so-called freedom of navigation operations under which US ships and aircraft challenge other countries' maritime claims.

Great to see Admiral Harry Harris nominated by @realDonaldTrump as US Ambassador to Australia. Look forward to seeing you in Canberra, Harry! pic.twitter.com/YHvu1NQ4BN — Malcolm Turnbull (@TurnbullMalcolm) February 10, 2018

He upset China by dubbing its construction of islands and building-up of military facilities in the South China Sea as a "great wall of sand".

Two deadly collisions involving US warships in the Pacific also occurred during his time as head of Pacific Command.

Ten sailors aboard the guided missile destroyer John S. McCain died when it collided with a tanker near Singapore on August 21.

Its sister ship, the Fitzgerald, almost sank off the Japanese coast on June 17 after colliding with a container ship. Seven crew died.

Two US officials, speaking on the condition of anonymity, said the Harris' likely replacement was Admiral Philip Davidson, commander of US Fleet Forces Command.

The officials did not comment on when an announcement could be made and any replacement will have to be approved by the US Senate.