Vietnam "resolutely opposes" Taiwanese leader Ma Ying-jeou's plan to visit Ba Binh (Itu Aba) island, the country's most senior official in Taiwan said Wednesday.
"If he goes it will raise tensions in the area," said Tran Duy Hai, chairman of the Vietnam Economic and Cultural Office in Taipei, the defacto embassy for Vietnam in the absence of official diplomatic ties.
Vietnam's opposition to the trip comes after the United States, a major ally of Taiwan, said the trip was "extremely unhelpful" and would not do anything to resolve disputes over the waterway.
Ma's office earlier announced that Ma, who steps down in May, would fly to Itu Aba on Thursday to offer Chinese New Year wishes to residents on the island, mainly Taiwanese coastguard personnel and environmental scholars.
Itu Aba was now the fourth largest island in the Truong Sa (Spratly) archipelago, which is claimed by Vietnam, after Mischief Reef, Fiery Cross Reef and Subi Reef.
Both Taiwan and China claim most of the South China Sea. Vietnam, the Philippines, Malaysia and Brunei have competing claims.