Speaking at a security conference in Singapore on Thursday, the deputy assistant secretary of state underscored a US desire to see the two sides resume talks frozen for four years.
Matthew Daley said his announcement reinforced "the point that American policy is not simply one of insisting on the status quo".
Analysts said the statement was really a warning to Taiwan that unilateral moves toward independence could destroy its economic and democratic "miracle".
No military solution
Washington has also warned President Chen Shui-bian to take China's threats of military retaliation seriously.
Assistant Secretary of State James Kelly said: "We in the United States see these risks clearly and trust they are well understood by (Chen) and others in Taiwan."
But Kelly also said that if China moved militarily against Taiwan, Bush's three-year-old promise to "do whatever it took" to defend Taiwan would come into play.
"A unilateral move towards independence will avail Taiwan of nothing it does not already enjoy in terms of democratic freedom, autonomy, prosperity and security"
assistant secretary of state
China continues to deploy intimidating missiles opposite Taiwan and refuses to renounce the use of force despite US pleadings that it should do so.
Kelly added the "one China" policy of having official relations with Beijing while maintaining unofficial ties with Taiwan had served the nation well for nearly three decades.
He also reiterated that the US does not support Taiwan independence.
"A unilateral move towards independence will avail Taiwan of nothing it does not already enjoy in terms of democratic freedom, autonomy, prosperity and security."