Washington: The suspected Chinese high-altitude surveillance balloon is expected to be over the US for a few days, Pentagon spokesperson Brigadier General Pat Ryder said.

"So as I mentioned, we'll continue to monitor it. Right now, we assess that it'll probably be over the United States for a few days, but we'll continue to monitor -- review our options and keep you updated as we can," Ryder said at a press briefing while responding to a media query.

Earlier, Ryder said that the balloon is above the central continental US right now and moving eastward.

"The balloon continues to move eastward and is over the center of the continental US. Again, we currently assess that the balloon does not present a military or physical threat to people on the ground at this time, and we'll continue to monitor and review options," he added.

Responding to a query on China's statement over the suspected balloon, Ryder said, "We are very aware of the PRC statement but however, but the fact is we know it is a surveillance balloon. We know that the balloon has violated US airspace and international law -- which is unacceptable. And we've conveyed this directly to the PRC on multiple levels."

Earlier, the Chinese Foreign Ministry said the balloon in the US is a civilian airship used for research, mainly meteorological.

"The airship is from China. It is a civilian airship used for research, mainly meteorological, purposes. Affected by the Westerlies and with limited self-steering capability, the airship deviated far from its planned course," China's Foreign Ministry said in a statement on the unintended entry of a Chinese unmanned airship into US Airspace.

The Chinese side "regrets the unintended entry of the airship into US airspace," it added. The Chinese side will continue to communicate with the US side and address this unexpected circumstance, the Foreign Ministry's statement said.

On Thursday, a Pentagon spokesperson, in an official briefing said, "The United States Government has detected and is tracking a high altitude surveillance balloon that is over the continental United States right now. The U.S. government, including NORAD, continues to track and monitor it closely. The balloon is currently traveling at an altitude well above commercial air traffic and does not present a military or physical threat to people on the ground. Instances of this kind of balloon activity have been observed previously over the past several years. Once the balloon was detected, the U.S. government acted immediately to protect against the collection of sensitive information."

Replying to a media query about whether they have contacted Chinese officials, Ryder said, "We have engaged PRC officials with urgency through multiple channels. They've been engaged both through their embassy here in Washington and through our embassy in Beijing."

The defence official said the balloon was recently over Montana and that officials were considering bringing the plane down with military assets, but decided against doing so because of the risks involved.