Analysis from several US defence and intelligence agencies found that the balloon carried commercially available US gear, along with more specialised Chinese sensors and other equipment to collect photographs, video and other information to transmit to China, the WSJ said, citing US officials.

The findings support a conclusion that the craft was intended for spying, and not for weather monitoring as China had claimed, the report said.

But the balloon did not seem to send data from its eight-day passage over Alaska, Canada and some other contiguous US states back to China, WSJ said.

The White House and the Federal Bureau of Investigation did not immediately respond to a request for comment.

In February, the US shot down the balloon, which had flown over sensitive military sites, sparking a diplomatic crisis.