Pelosi, a long-time China critic, was expected to arrive in Taipei later on Tuesday, people briefed on the matter said, as the United States said it would not be intimidated by Chinese warnings over the visit.
The carrier USS Ronald Reagan had transited the South China Sea and was currently in the Philippines Sea, east of Taiwan and the Philippines and south of Japan, a U.S. Navy official told o Reuters.
The Japan-based Reagan is operating with a guided missile cruiser, USS Antietam, and a destroyer, USS Higgins.
"While they are able to respond to any eventuality, these are normal, routine deployments," said the official, who spoke on the condition of anonymity.
They would not comment on precise locations.
The official said the amphibious assault ship USS Tripoli was also in the area.
Signs emerged of military activity on both sides of the Taiwan Strait ahead of Pelosi's visit.
Chinese planes flew close to the median line dividing the waterway on Tuesday morning and several Chinese warships had remained close to the unofficial dividing line since Monday, a source briefed on the matter told Reuters.
China's defense and foreign ministries did not immediately respond to requests for comment.