Taiwan urged the United States Monday to honour an agreement to supply submarines to replace its current elderly fleet, as a US congressional group visited the island to evaluate defence needs.

President Ma Ying-jeou voiced the desire while meeting the group led by Edward Royce, chairman of the US House Committee on Foreign Affairs.

"The two Guppy-class (submarines) joined the Taiwan force more than 40 years ago when I was with the navy. Now indeed they are very old and need to be replaced," Ma told his guests.

He was referring to two diesel-electric submarines built in the 1940s, which the US congressmen saw while travelling to the island's southern Tsoying naval base Sunday.

After being retired by the US navy, the vintage warships were sold to Taiwan in 1973 and have since been used for naval training.

The United States remains the leading arms supplier to Taiwan despite switching diplomatic recognition from Taipei to Beijing in 1979.

In April 2001 then-President George W. Bush approved the sale of eight conventional submarines as part of Washington's most comprehensive arms package for the island since 1992.

Since then, however, there has been little progress in filling the order.

The United States has not built conventional submarines for more than 40 years and Germany and Spain reportedly declined to offer their own designs for fear of offending China.

Royce told reporters his group had held talks with Taiwanese admirals about possible ways to remove barriers to the arms deal, but did not elaborate.

The Taiwanese navy currently has two other submarines which are Dutch-built, and these are the only ones which could be deployed in case of war.

Tensions between Taiwan and China have eased markedly since Ma came to power on a platform of strengthening trade links and allowing more Chinese tourists to visit. He was re-elected in January.

But Taiwan, which has governed itself since 1949, still sees the need to modernise its armed forces. China regards the island as part of its territory awaiting reunification, by force if necessary.