AN exhausted Australian sailor has been rescued in the middle of the Pacific Ocean.

A cargo ship picked up Juan Dario Zea Restrepo about 425 nautical miles off Christmas Island in the Republic of Kiribati on Monday night (US time).

He is now aboard Singaporean container vessel, Kota Wangi, which is making its way towards Melbourne.

The 58-year-old mariner was sailing from California to Christmas Island, in the Republic of Kiribati, when his vessel's autopilot reportedly failed.

The US Coast Guard said Mr Restrepo had been manually navigating his 19x4m vessel, Folly II, for four weeks and called for help after becoming too tired to continue.

On April 6, Mr Restrepo, who it is understood has been living in Colombia, told friends on Facebook that he planned to reach Australia by September.

"Ready my sailboat out of California to Kiribati, are about 5,000 kms and me it takes 4 to 6 weeks, without connection to the internet, but connected to the stars... I reach Australia for September (sic) ... well, I hope you continue doing the same thing! do not change... ," he posted.

In his profile on a sailing website Mr Restrepo described himself as a "greenie sailor".

"I love freedom, interested in conserving our seas, fauna and flora, history and traditions, Colombian," he said.

"I sailed from Fraser Island, Australia to SEA 4 years solo 8.000 miles. now I want to circumnavigate."

Watchstanders in Coast Guard Joint Rescue Coordination Centre Honolulu received a distress notification from the Personal Locator Beacon on Mr Restrepo's vessel at about 6am on Monday.

The Coast Guard sent a HC-130 plane from Air Station Barbers Point in Hawaii to establish communications with the mariner.

A second HC-130 provided cover during the rescue.

The Kota Wangi rescued Mr Restrepo in the North Pacific at 9pm on Monday.

"He was picked up last night. He was in good condition. He didn't have any injuries reported," a Coast Guard spokesman told news.com.au.

The Folly II was abandoned.

The Kota Wangi is registered with a network of ships whose crews volunteer to help with ocean rescues.

Christmas Island is more than 1300 nautical miles south of Honolulu. It is not to be confused with Christmas Island in the Indian Ocean where Australia processes asylum seekers.

Additional reporting AP