WASHINGTON — U.S. Secretary of State Antony Blinken will postpone his planned trip to Beijing after the U.S. detected a Chinese surveillance balloon hovering over Montana.

A senior State Department official said Friday that despite the Chinese government claiming the balloon had entered U.S. airspace accidentally, its presence was a “clear violation of sovereignty.”

The Pentagon press secretary confirmed midday Friday that the balloon is now over the center of the U.S. and people can look up and see it. He told reporters that we’re “not going to get into an hour by hour location of the balloon.”

The balloon does not pose a “physical or military risk to people on the ground,” said Brig. Gen. Pat Ryder, the Pentagon press secretary.

He added that what makes this different from similar events “is the duration and length of which it has been over U.S territory.”

President Joe Biden was briefed about the balloon Tuesday, according to White House press secretary Karine Jean-Pierre.

Ryder said midday Friday that the balloon was traveling at an altitude of 60,000 feet and was expected to remain over the U.S. “for a few days.”

Ryder said the balloon is “maneuverable” and “has changed course,” but would not answer reporters’ questions about a specific location or when the aircraft changed its position.

U.S. Sen. Roger Marshall, of Kansas, early Friday afternoon posted to Twitter that the balloon was over his state.

“I can confirm the Chinese spy ballon (sic) is over NE KS. My staff is in contact with law enforcement officials,” he wrote. “I condemn any attempts the Chinese make to spy on Americans. President Biden must protect the sovereignty of the U.S. whether it’s our airspace or the southern border.”

The Pentagon did not immediately answer an inquiry to confirm Marshall’s assertion.

A Chinese foreign ministry spokesperson on Friday characterized the vehicle as a civilian airship used for meteorological research that deviated from its planned flight path.

“The Chinese side regrets the unintended entry of the airship into US airspace due to force majeure,” the spokesperson said in a statement — in other words, an action that could not be anticipated or controlled.

Blinken was scheduled to depart for Beijing Friday night for what was meant to be a wide-ranging meeting with Chinese counterparts following President Joe Biden’s November meeting in Bali with China President Xi Jinping.

However, after consultations with the Pentagon and Congress, the State Department concluded that “conditions are not right at this moment for Secretary Blinken to travel to China,” the senior State Department official said, speaking to reporters on background.

Montana’s U.S. Sen. John Tester said Friday morning that he has been monitoring the situation.

“I am in contact with DOD and Intelligence officials about this completely unacceptable provocation,”? Tester wrote on Twitter early Friday. “I am receiving a classified briefing once I return to Washington and will hold everyone accountable until I get real answers.”

The Pentagon confirmed Thursday that the U.S. had detected and begun tracking the balloon, which is traveling at a high altitude, “well above commercial air traffic and does not present a military or physical threat to people on the ground,” according to Ryder.

“Instances of this kind of balloon activity have been observed previously over the past several years. Once the balloon was detected, the U.S. government acted immediately to protect against the collection of sensitive information,” Ryder said.

The “sizable” balloon entered U.S. continental airspace “a couple of days ago,” a Pentagon senior official told reporters Thursday.

The official said the Pentagon is “very confident” the balloon belonged to the People’s Republic of China and that the U.S. gained custody of the balloon when it entered U.S. airspace.

Officials decided not to shoot it down because of the risk to people and private property below, the senior official said.

The balloon is carrying a “payload” underneath, which Ryder described as surveillance equipment but would not give further details.

“It is big enough that, in reviewing our approach, we do recognize that any potential debris field would be significant and potentially cause civilian injuries or deaths, or significant property damage,” Ryder said Friday.

The balloon was spotted within days of a Montana state Legislature hearing on a bill that would prevent foreign adversaries from buying up agricultural land in Montana, States Newsroom’s Daily Montanan reported.

Montana is one of the several sites where U.S. nuclear missiles are based.

This article has been updated with Pentagon comments and news of more sightings.