"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 Pentagon said Thursday it was tracking a Chinese spy balloon flying high over the United States, with a senior defence official telling reporters that "the intent of this balloon is for surveillance".

At President Joe Biden's request, US officials considered shooting the balloon down but concluded doing so would endanger too many people on the ground, the official said on condition of anonymity.

The incident came just days before a scheduled visit to China by US Secretary of State Antony Blinken aimed at managing heightened tensions between the two powers.

The visit will mark the first trip to the Asian country by the United States' top diplomat since 2018.

Beijing did not immediately identify the balloon's Chinese origins at a foreign ministry news briefing on Friday.

It made the admission later, saying the civilian craft was blown off course.

"Affected by the Westerlies and with limited self-steering capability, the airship deviated far from its planned course," the statement said.

"The Chinese side will continue communicating with the US side and properly handle this unexpected situation caused by force majeure," it said.