"I expect to be speaking with President Xi and... we're going to get to the bottom of this," Biden said in his most extensive public remarks since the incident on Feb. 4.
While stressing that the U.S. is "not looking for a new Cold War," Biden said "I make no apologies for taking that down balloon."
"We'll always act to protect the interests of the American people and the security of the American people," Biden said.
The U.S. has been in a state of alarm since the huge white balloon from China was spotted tracking over a series of top-secret nuclear weapons sites, before being shot down just off the East Coast.
Biden said there is no evidence there has been a sudden increase in the number of objects in the skies over America, explaining after the Chinese spy balloon was shot down, radar was enhanced to pick up more slow-moving objects.
The U.S. military discovered three more unidentified craft that Biden ordered shot down — one over Alaska, another over Canada and the third over Lake Huron off Michigan.
China says the balloon was just a stray weather research craft, but U.S. officials say they have conclusive evidence that the balloon was sent to spy.
The incident has prompted a diplomatic rift, with Secretary of State Antony Blinken abruptly canceling a rare visit to China. Beijing accused Washington of overreacting and claimed that U.S. balloons had overflown Chinese territory, something the Biden administration denies.
Biden drew a clear distinction between the Chinese balloon and the three smaller objects shot down afterwards.
"We don't yet know exactly what these three objects were," Biden said, while ruling out Chinese involvement — and suggesting they could be civilian craft of some kind.
"Nothing right now suggests they're related to China's spy balloon program or... surveillance vehicles from any other countries," Biden said.
"The intelligence community's current assessment is that these three objects are most likely balloons tied to private companies" or research projects, he said.
However, "if any object presents a threat to the safety, security (of) the American people I will take it down," Biden said.
VOA's Steven Herman contributed to this report.