White House National Security Council spokesman John Kirby underlined Monday that Pelosi has the final say on whether or not to visit the self-governing island.
He said US lawmakers have been visiting Taiwan regularly for years. China claims Taiwan.
Kirby said administration officials are concerned that Beijing may use the visit as an excuse to take military action in the Taiwan Straits or around Taiwan.
Earlier on Monday, China said it was closely monitoring reports of Pelosi's plans to travel to Taiwan.
It also warned the US that if Pelosi travels to Taiwan, its military will react "sternly" and face "serious consequences".
Pelosi is likely to travel to Taiwan despite warnings.
Responding to reports of Pelosi's visit to Taiwan, Chinese Foreign Ministry spokesman Zhao Lijian told reporters in Beijing,
"We are monitoring Pelosi's schedule closely and will respond strongly if she travels to Taiwan."
No official announcement has been made regarding Pelosi's visit to Taiwan, but local media in Taiwan reported that Pelosi would arrive in the capital Taipei on Tuesday night.