"China's remarks on Taiwan raise a serious question. It's not in our interest to let China acquire extreme economic clout in the region. We will look into this issue as we work on a new China strategy that will be published next year," she said.
US House of Representatives speaker Nancy Pelosi arrived in Taipei earlier on Tuesday, despite warnings from China that the United States was "playing with fire."
Beijing sees Taiwan as its territory and any unauthorized visit to the island in the South China Sea as a challenge to its One-China policy.