WASHINGTON, Feb 3 (AFP) - US Secretary of State Antony Blinken postponed a visit to China that had been expected to start on Friday (Feb 3) after a suspected Chinese spy balloon was tracked flying across the United States in what Washington called a "clear violation" of US sovereignty.

The Pentagon said on Thursday it was tracking a high-altitude surveillance balloon over the continental United States. Officials said military leaders considered shooting it down over Montana on Wednesday but eventually recommended against this to President Joe Biden because of the safety risk from debris.

White House spokesperson Karine Jean-Pierre said Biden was briefed on the balloon flight on Tuesday and there was an administration "consensus that it was not appropriate to travel to the People's Republic of China at this time".

China earlier expressed regret that what it called a "civilian airship had strayed into US territory after being blown off course."

The administration was aware of China's statement "but the presence of this balloon in our airspace, it is a clear violation of our sovereignty as well as international law. It is unacceptable this occurred," she told a regular briefing.

On Friday, Pentagon spokesman Brigadier General Patrick Ryder said the balloon had changed course and was now floating eastward at about 18,300m above the central United States and demonstrating a capability to maneuver. He said it would likely be over the country for a few more days.

The Pentagon's disclosure about the balloon's maneuverability directly challenges China's assertion about the balloon being blown off course.

At a news conference with South Korea's visiting foreign minister later on Friday, Blinken said he had told Wang Yi, director of China's Central Commission for Foreign Affairs, that the incident on the eve of his trip was an "irresponsible act" by China, but Washington remained committed to engagement and he would visit when conditions allowed.

Blinken said he was not going to put a date on when he might go to China and the focus was on resolving the current incident. “The first step is ... getting the surveillance asset, out of our air space,” he said, adding that the United States would continue to maintain open lines of communication with China.

The Republican chairman of the House of Representatives Foreign Affairs Committee, Michael McCaul, said the balloon should never have been allowed in US airspace and could have been shot down over water.

"I am calling on the Biden administration to quickly take steps to remove the Chinese spy balloon from US airspace," he said in a statement.