The United States is deeply worried that Taiwanese President Chen Shui-bian is moving toward independence for the island as he wages a high-stakes re-election campaign, despite an unusual public rebuke from President George W. Bush.
Senior US officials recently have seen indications that Taiwanese voters, responding to US concerns, may be growing sceptical of a controversial referendum sought by Chen, which has angered China.
Chen has said the referendum would call for China to remove 500 missiles aimed at Taiwan, although the exact language of the ballot question has not yet been made public.
It is seen as a sign Chen may want to change the delicate status of the democratic, self-ruling island, which split from the mainland after a civil war in 1949.
Beijing has threatened to attack the island if it claims statehood. So far Chen has not backed down and has done nothing to reassure Washington, which fears a Taiwan-China crisis if the referendum goes forward on Mar. 20, US officials say. Chen is also up for re-election that day.
"There have been more and more signs that Chen wants to change the status quo on Taiwan and that is worrisome," one senior US official told Reuters.
"Six months ago, I don't think anybody here (in Washington) was seriously thinking that that was what he was planning. Now, I don't think there is anybody here who doesn't have doubts," said the official, who spoke on condition of anonymity.
Reflecting US anxiety, Bush, with Chinese Prime Minister Wen Jiabao at his side in the Oval Office, last month bluntly warned Chen against changing Taiwan's status quo with China.
Beijing considers the self-ruled island a renegade province that someday must be unified with the mainland, by force, if necessary. Washington is Taiwan's main arms supplier and trading partner.
In their meeting, Bush also warned Wen against China taking unilateral steps on Taiwan and reaffirmed a US commitment to "get involved" if Beijing acted militarily against the island. But Taiwan remains the key US concern.