Koror (Palau) (AFP) - The United States has announced plans to install radar systems in Palau, a move that will increase its monitoring ability in the western Pacific region recently rocked by threats from North Korea.

In a joint statement, the US Defense Department and the Palau government said they were working to finalise the location of radar towers on the archipelago nation of 22,000 people.

"The radar systems will provide Palau enhanced maritime law enforcement capability... while also providing the US with greater air domain awareness for aviation safety and security," they said in the statement dated August 21.

While Palau is an independent nation, it has no military and the US is responsible for its defence under an agreement with Washington.

Under the deal, the US military has access to the islands, although it currently has no troops stationed there.

Palau is about 1,300 kilometres (800 miles) south-west of Guam, the US Pacific territory that Pyongyang threatened to fire missiles towards earlier this month, sparking rhetoric of "fire and fury" from President Donald Trump.

The statement said the US proposed the radar installation on July 18, before the recent crisis with North Korea erupted.

"This project is essential to the well-being of the Republic of Palau's air and maritime domains, as well as to the ability of the United States to maintain its defence of the Republic of Palau," it said.

"The sites provided (for radar towers), which have yet to be finalised, have been chosen with an eye on minimising environmental impacts."

Both the Palau government and the US embassy in Koror declined to comment further.

The radar system would help Palau monitor a massive 500,000-square-kilometre (193,000-square-mile) maritime sanctuary it created in 2015.

The sanctuary -- approximately the size of Spain -- is difficult for Palau to police for illegal fishing.