The tiny Pacific nation of Palau has welcomed a pledge from Japanese charities to supply a large patrol boat to help stamp out illegal fishing.

Palau last year created a vast marine sanctuary the size of Spain but has only one long-range patrol boat to enforce the 500,000 square kilometre (193,000 square mile) no-fishing zone.

President Tommy Remengesau said two Japanese non-government organisations -- Nippon Foundation and the Sasakawa Peace Foundation -- had agreed to help out.

He said they would supply a 40-metre (130-foot) patrol boat, as well as covering fuel and maintenance costs, in a project expected to cost more than US$30 million.

"With this assistance... I believe that we are well on the way to developing one of the largest and the best protected marine sanctuaries on our planet," Remengesau said at a recent ceremony in Koror.

He said the boat was expected to be handed over by the end of next year.

Palau's sanctuary will be phased in over five years, eventually leaving only a relatively small area of its waters open to fishing by locals but not the foreign trawlers that dominate the Pacific industry.

The no-fishing plan prioritises tourism -- which contributes about US$160 million or 50 percent of gross domestic product annually -- over the tuna industry, which contributes around US$5.5 million a year.

It is not the first time Palau, which has a population of just 18,000, has led the world on maritime conservation.

It created the world's first shark sanctuary in 2009 and about one-third of countries have now followed suit, changing attitudes to the predator and helping curb demand for shark fin soup.