By Yashwant Raj Washington, Feb 3 : The US has said that it was closely monitoring a Chinese spy balloon that is said to be the size of three passenger buses wafting across the sky and it has considered shooting it down but has hesitated so far fearing falling debris on civilian populations underneath. This is not the first such sighting. It's happened before, but the US defense department said this is the longest Chinese spy balloon that has been seen hovering over the country. And it comes as Secretary of State Antony Blinken prepares to visit China and President Joe Biden is slated to deliver his first State of the Union speech in a Republican-led House of Representatives. India will be following this spy balloon's flight as well for insights and lessons given its own border challenges with China, whose military has provoked a string of skirmishes along the Line of Actual Control in recent years, the last of them took place in December, and with increasing frequency. "The United States government has detected and is tracking a high-altitude surveillance balloon that is over the continental United States right now," Pentagon Press Secretary Air Force Brigadier Gen. Pat Ryder said during an impromptu briefing on Thursday evening. "The US government, to include NORAD (North American Aerospace Defense Command), continues to track and monitor it closely." But the balloon poses no threat to commercial air traffic as it's positioned way above that height, Ryder said. President Biden has been briefed, according to news reports. A senior defence official who briefed reporters on background that the US intelligence community has "very high confidence" the balloon belong to China and the US has engaged China on it "with urgency, through multiple channels". The US is weighing options on how to deal with the balloon but for now, the official said, it's been decided at the highest level in the US military - Chairman of joint chiefs of staff Mark Milley - to let it float overhead, rather than to shoot it down. The key concern being the safety of civilians down below. "We did assess that it was large enough to cause damage from the debris field if we downed it over an area," the official said. "I can't really go into the dimension a"Abut there have been reports of pilots seeing this thing, even though it's pretty high up in the sky. So ... it's sizable." But the US is largely leery of the mission of this spy mission. "Currently, we assess that this balloon has limited additive value from an intelligence collective collection perspective," the official said. "But we are taking steps, nevertheless, to protect against foreign intelligence collection of sensitive information." /IANS