The US Coast Guard on Monday imposed a temporary security zone in waters off South Carolina during the military's search for debris from a suspected Chinese spy balloon shot down by a US fighter jet, and the White House said it would keep a calm approach to relations with Beijing.

President Joe Biden told reporters it was always his view that the balloon needed to be shot down and brushed off a question about whether the incident would weaken US-China relations.

"No. We made it clear to China what we're going to do,” he said. “They understand our position. We're not going to back off. We did the right thing and it's not a question of weakening or strengthening - it's reality.”

White House national security spokesperson John Kirby said the balloon's flight over the United States had done nothing to improve already tense relations with China and dismissed Beijing's contention it was for meteorological purposes.

White House press secretary Karine Jean-Pierre nevertheless said the US approach to relations with China would remain calm and it was up to China to decide whether it wanted to build on a meeting between Biden and Chinese President Xi Jinping last November.

"It's up to China to figure out what kind of relationship they want,” she said.

The appearance of the Chinese balloon caused a political uproar in the United States and prompted the top US diplomat, Antony Blinken, to cancel a February 5-6 trip to Beijing that both countries hoped would steady their rocky relations.

Beijing condemned the shooting down of the balloon as an "obvious overreaction” and urged Washington to show restraint.

"China firmly opposes and strongly protests against this,” Vice Foreign Minister Xie Feng said in remarks to the U.S. Embassy in Beijing posted on the ministry's website.

When asked on Tuesday whether China had asked the United States to return the debris from the downed balloon, Chinese foreign ministry spokesperson Mao Ning said the balloon belonged to China.

"This balloon is not American. The Chinese government will continue to defend its legitimate rights and interests,” she said at a regular presser.

Mao also said she did not have more information on what equipment the balloon was carrying.

The ministry said on Monday that China learned its balloon had drifted over the United States after being notified by Washington.

While urging US restraint, China has also warned of "serious repercussions” and said it will use the necessary means to deal with “similar situations,” without elaborating. Some policy analysts said they expect any response to be finely calibrated, however, to prevent diplomatic ties becoming even worse.

Some US Republicans have questioned why the balloon was not shot down before it was allowed to travel across the United States. Biden asked for military options last Tuesday, according to U.S. officials, but Pentagon officials said the risks were too great to shoot it down over land.

"Once it came over the United States from Canada, I told the Defense Department I wanted to shoot it down as soon as it was appropriate,” Biden told reporters.“They concluded ... we should not shoot it down over land. It was not a serious threat and we should wait until it got across the water.”

After first passing into US airspace north of Alaska's Aleutian Islands on January 28, the balloon was downed off the US Atlantic Coast on Saturday - a week later.

Kirby said Blinken would seek to reschedule his trip, the first by a U.S. secretary of state to Beijing since 2018, when the time was right. State Department spokesperson Ned Price said Washington and Beijing had not had conversations about this.

Intelligence gathering

US officials have played down the balloon's impact on national security, but say a successful recovery could give the United States insight into China's spying capabilities.

Kirby said United States was able to study the balloon while it was aloft and officials hope to glean valuable intelligence on its operations by retrieving as many components as possible.

Senior US officials have offered to brief former Trump administration officials on the details of what the White House said were three China balloon overflights when Donald Trump was president. US officials said those balloons came to light after Trump left office in January 2021 and was succeeded by Biden.

A senior US general responsible for bringing down the balloon said on Monday the military had not detected previous spy balloons before the one that appeared on January 28 over the United States and called it an “awareness gap.”

However, Air Force General Glen VanHerck, head of US North American Aerospace Defense Command and Northern Command, said US intelligence determined the previous flights after the fact based on “additional means of collection” of intelligence without offering further details on whether that might be cyber espionage, telephone intercepts or human sources.

Chinese foreign ministry said another balloon, spotted over Latin America, was an unmanned civilian airship on a test flight that “severely deviated and unintendedly entered the space above Latin America because it was affected by the weather and because it has limited self-steering capability.”

On Sunday, Colombia's military said it sighted an airborne object similar to a balloon after the Pentagon said on Friday another Chinese balloon was flying over Latin America.