"The airship is from China," a spokesperson for China's Ministry of Foreign Affairs said in a statement. "It is a civilian airship used for research, mainly meteorological, purposes."
"The Chinese side regrets the unintended entry of the airship into US airspace due to force majeure," the statement said.
The PRC statement came after the Pentagon stated bluntly that "The United States government has detected and is tracking a high-altitude surveillance balloon that is over the continental United States right now"
The U.S. has been observing it with piloted military aircraft, one of the officials told reporters on condition of anonymity.
After President Joe Biden requested military options, Defense Secretary Lloyd Austin and top military officials considered shooting the balloon down, a senior defense official told reporters Thursday.
But they decided doing so would endanger too many people on the ground, and because they assessed the balloon did not pose a threat to civilian aviation, the official said.
"Clearly, the intent of this balloon is for surveillance," said the official, who spoke on condition of anonymity.
The official added that the balloon had flown over the northwest United States, where there are sensitive airbases and nuclear missiles in underground silos, but that the Pentagon did not believe it constituted a particularly dangerous intelligence threat.
"We assess that this balloon has limited additive value from an intelligence collection perspective," the official said.
The official added that there was "no doubt" the balloon was Chinese, without explaining why.
Following Beijing's "sorry" statement, Washington announced that US Secretary of State Antony Blinken will travel to China when "conditions are right."
The official, speaking on condition of anonymity, said that a row over an alleged Chinese spy balloon "would have significantly narrowed the agenda" for Blinken had he gone ahead with his planned weekend departure to PRC.
Separately, Canada's defense ministry said a "high-altitude surveillance balloon" was detected and that it was monitoring a "potential second incident", without giving further details, adding that it was in frequent contact with the United States.
This report was produced using Reuters and Agence France-Presse.