The United States will not set any preconditions for President Joe Biden to speak with Chinese President Xi Jinping, the White House said Friday, amid heightened tensions over a suspected Chinese spy balloon.

White House national security spokesman John Kirby said in a press briefing that Biden will hold a conversation with Xi "when the president believes it's appropriate," adding that Washington's lines of communication with Beijing remain open.

However, he noted that military-to-military channels between the two countries remain closed, and "that's really what we would like to see amended."

U.S. President Joe Biden (L, Getty/Kyodo) and Chinese President Xi Jinping. (Kyodo)

No formal request for a conversation between the leaders has been made as yet by the United States, Kirby added in response to a question from a reporter.

The spokesman's comments came a day after Biden told reporters that he expects to be speaking with Xi and added "I hope...we are going to get to the bottom of this. But I make no apologies for taking down that balloon."

For the first time since taking office, Biden held an in-person meeting with Xi in November on the sidelines of a Group of 20 summit in Indonesia, with the two agreeing to facilitate communication despite disagreements on many issues.

But the giant balloon, suspected of carrying out espionage over the United States, has become a new flashpoint between the two countries. U.S. forces shot the object down on Feb. 4 off the coast of South Carolina, infuriating China.

The U.S. military said the recovery operations for the Chinese balloon, which was the size of about three buses and capable of collecting signals intelligence, concluded Thursday off the coast.

"Final pieces of debris are being transferred to the Federal Bureau of Investigation Laboratory in Virginia for counterintelligence exploitation, as has occurred with the previous surface and subsurface debris recovered," the U.S. Northern Command said in a statement on Friday.

It said all naval and coast guard vessels have departed the area, and air and maritime safety perimeters have been lifted.

U.S. officials believe the balloon, which they said flew near "sensitive" defense sites, was linked to the Chinese military, but Beijing has insisted it was a civilian craft being used for weather research and was accidentally blown off course by strong winds.

In his most extensive comments about the balloon, Biden said Thursday nothing so far suggests that three unidentified aerial objects subsequently shot down by the military were related to spying by China.

Biden told reporters at the White House that the three objects were most likely tied to "private companies, recreation or research institutions," based on the intelligence community's current assessment.

Kirby said the United States was facing "tough" weather and environmental conditions in retrieving the objects after they were brought down last week in Alaska, Canada's Yukon territory and Lake Huron in Michigan, respectively.

The U.S. command released a statement late Friday night saying it had ended search operations for the two objects near Deadhorse, Alaska, and the one at Lake Huron as its "activities have discovered no debris."

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