"Taiwan is a democratic entity that will have to make its own decisions but I think we have been very clear that we think that this referendum is not going to help anyone and in fact it shouldn't be held," Rice told reporters when she visited Beijing two weeks ago.
China's Foreign Minister Yang Jiechi acknowledged Washington's opposition to Taiwan's UN referendum plans, calling the Taiwan question "the biggest concern of China."
Taiwan does not have a seat at the UN. The island is formally recognized by 23 countries, compared with the 170 that recognize China.
Taiwan's bid for recognition is unlikely to pass in the UN, even if it wins favor among Taiwanese voters.
Taiwan's election results are crucial, especially with respect to relations with China and the United States. On March 22, the Taiwanese will not be the only ones waiting to see who their next president will be.