Large Chinese reconnaissance balloon spotted over the US, officials say

A massive spy balloon believed to be from China was seen above Montana and is being tracked as it flies across the continental United States, with President Joe Biden for now deciding against "military options" because of the risk to civilians, U.S. officials said on Thursday.

Still, officials insisted, they continue to closely monitor the vessel as they have since it entered the country -- while voicing their concern to Beijing.

"The United States government has detected and is tracking a high-altitude surveillance balloon that is flying over the continental United States right now," Brig. Gen. Pat Ryder said in a statement on Thursday. "NORAD [North American Aerospace Defense Command] continues to track and monitor it closely."

MORE: Chinese balloon live updates

NORAD later said in a statement that its commander, Gen. Glen VanHerck, "assesses the balloon does not present a military or physical threat to people on the ground at this time. The balloon is currently traveling at altitude well above commercial air traffic."

The Canadian Department of National Defence and the Canadian Armed Forces are working with NORAD and "other partners" to assess the situation, the agency said in a statement, adding that Canada is "taking steps to ensure the security of its airspace, including the monitoring of a potential second incident."

A U.S. official told ABC News on Friday that, due to the balloon, Secretary of State Antony Blinken will delay his upcoming trip to Beijing, originally scheduled for next week. The official noted that Blinken did not want to blow the situation out of proportion by cancelling his visit, but also does not want the balloon to dominate his meetings with Chinese officials.

The high-altitude reconnaissance balloon was not the first such craft to pass over the U.S. in this way, a senior defense official said in a briefing.

A separate senior official told ABC News the balloon is the size of three buses and complete with a technology bay, which the defense official said they "wouldn't characterize" as "revolutionary."

The defense official said they "are confident" the balloon was sent by China.

"Instances of this activity have been observed over the past several years, including prior to this administration," the official said, noting that "it's happened a handful of other times over the past few years ... It is appearing to hang out for a longer period of time this time around."

Beijing's first official response to the balloon came Friday, with Chinese Ministry of Foreign Affairs spokesperson Mao Ning telling reporters that authorities are still "gathering the facts."

"I want to stress that, before it becomes clear what happened, any deliberate speculation or hyping up will not help," Mao said during a routine press conference. "The Chinese side is gathering the facts and hopes all sides will handle this matter in a cool-headed manner."

"We act in accordance with international law," she added. "We have no intention to violate other country's sovereignty and bearing the facts, we hope relevant parties would and would handle the matter in a clear-headed way."

When asked whether the balloon would affect Blinken's expected visit to Beijing next week, Mao told reporters: "I have nothing to share at this moment."

Later Friday, following the news that Blinken would delay his visit, the Chinese Foreign Ministry posted an updated statement on its website, admitting that the "airship comes from China" but "is of a civil nature and is used for meteorological and other scientific research."

"Affected by the westerly belt and its own limited control ability, the airship seriously deviated from the predetermined route," the ministry added. "China regrets that the airship strayed into the United States due to force majeure. China will continue to maintain communication with the United States to properly deal with this unexpected situation caused by force majeure."

"Force majeure" refers to something that is done beyond the control of the government.

One outside expert predicted the balloon could be essentially scientific and set off course, though other sources said it appeared to be "purposeful."

Retired Col. Steve Ganyard, an ABC News contributor, said the balloon looked to be a standard research vessel -- which would mean it was unpowered and drifted with the jet stream.

A senior U.S. official, however, told ABC that the military balloon was specially designed, with a purposeful path. They believe the balloon can take high-resolution pictures and is flying along areas where there are missiles and bases.

Echoing that, the defense official told reporters: "I'm not trying to be a wise guy, but the goal was surveillance and clearly they're trying to fly this balloon over sensitive sites ... to collect information."

The defense official said the U.S. had used "multiple channels" to tell China how seriously they are taking this incident. "We have made clear we will do whatever is necessary to protect our people and our homeland," said the official, who added that if the risk does increase then "we will have options to deal with this balloon."

Biden was briefed about the balloon and "asked for military options," the defense official said. The president agreed with the recommendation of the chairman of the Joint Chiefs of Staff, Gen. Mark Milley, and U.S. Northern Command Gen. Glen D. VanHerck to not "take kinetic action due to the risk to safety and security of people on the ground from the possible debris field."

A senior administration official echoed that view and said in a statement, "We acted immediately to protect against the collection of sensitive information."

A U.S. official said Thursday night that the U.S. is closely monitoring the situation with the balloon and "keeping all options open."