Taiwan's vice president left Monday for a stopover in the United States on a trip considered a test of a "diplomatic truce" with China which has previously protested over such visits.

Wu Den-yih was due to stop in New York before flying on to the Dominican Republic, where he will take part in the presidential inauguration of Danilo Medina, the presidential office said in a statement, adding that he would also visit Belize.

"The brief stay in New York is purely a transit," foreign ministry spokesman Steve Shia told AFP, in an apparent bid to keep the trip low profile.

Wu will transit in Los Angeles on his return from his 12-day tour.

Beijing insists Taiwan is part of its territory and opposes any overseas visit by Taiwanese officials. It was not clear if Beijing would lodge a complaint with Washington over Wu's stopover.

China repeatedly protested to Washington over US transit stops made by President Ma Ying-jeou's predecessor Chen Shui-bian, who irked Beijing with his confrontational pro-independence rhetoric.

But relations have improved dramatically since Ma, of the China-friendly Kuomintang, came to power in 2008 on a platform of beefing up trade and tourism links. He was re-elected in January for a second and last four-year term.

Observers see Wu's trip as a test of Ma's policy of maintaining a "diplomatic truce" with China, aiming to end a decades-old rivalry that saw the two former rivals seeking to lure allies away from each other.

Both sides had accused each other of using generous financial packages to ensure the loyalty of governments or persuade them to switch allegiance, especially in Africa, Latin America and the Pacific.

Only 23 nations formally recognise Taipei over Beijing.