President Joe Biden said on Thursday he expects to speak with China's President Xi Jinping about what the United States says was a Chinese spy balloon that a US fighter jet shot down early this month after it transited the United States.

"We are not looking for a new cold war," Biden said.

Biden, in his most extensive remarks about the Chinese balloon and three unidentified objects downed by American fighters, did not say when he would speak with Xi, but said the United States was continuing to engage diplomatically with China on the issue.

"I expect to be speaking with President Xi, I hope we are going to get to the bottom of this, but I make no apologies for taking down that balloon," said Biden in response to complaints from Beijing.

China says the 60-metre balloon was for monitoring weather conditions, but Washington says it clearly was a surveillance balloon with a massive undercarriage containing electronics.

Biden, who had offered few public comments about the spate of aerial objects that began with the Chinese balloon, broke his silence after lawmakers demanded more information on the incidents, which have baffled many Americans.

He said the US intelligence community was still trying to learn more about the three unidentified objects: one that was shot down over Alaska, one over Canada and a third that plunged into Lake Huron.

"We don't yet know exactly what these three objects were, but nothing right now suggests they were related to the Chinese spy balloon programme, or they were surveillance vehicles from other any other country," he said.

Biden said the objects might have been spotted due to enhanced radar in response to the Chinese balloon and that he and his team were working on new parameters on when to launch missiles at such aircraft.

The intelligence community believes the three objects were "most likely balloons tied to private companies, recreation or research institutions," Biden said. (Reuters)