China said Tuesday it will “resolutely safeguard its legitimate rights and interests” over the shooting down of a suspected Chinese spy balloon by the United States, as relations between the two countries deteriorate further. The balloon prompted US Secretary of State Antony Blinken to cancel a highly-anticipated visit to Beijing this week that had offered slight hopes for an improvement in relations, AFP said. China claims it was a civilian balloon used for meteorological research but has refused to say to which government department or company it belongs. Foreign Ministry spokesperson Mao Ning on Tuesday reiterated that the “unmanned airship” posed no threat and entered US airspace accidentally. Mao again criticized the US for overreacting rather than adopting a “calm, professional" manner, and for using force in bringing the balloon down Saturday in the Atlantic Ocean just off the US coast. Asked if China wanted the debris returned, she only reasserted that the balloon “belongs to China." “The balloon does not belong to the US. The Chinese government will continue to resolutely safeguard its legitimate rights and interests," Mao said at a daily briefing without giving further details. Beijing's attitude has hardened considerably following a surprisingly mild initial response on Friday, in which it described the balloon's presence as an accident and expressed “regret" for the balloon having entered the US. Subsequent statements have grown firmer, in the same tone used to confront the US over issues from Taiwan to trade, technology restrictions and China's claim to the South China Sea. China says it lodged a formal complaint with the US Embassy in Beijing, accusing Washington of having “obviously overreacted and seriously violated the spirit of international law and international practice." Recent developments have laid bare the extremely fragile nature of what many had hoped could be a manageable economic, political and military rivalry. US-China tensions have stirred deep concern in Washington and among many of its allies. They worry that outright conflict could have a strong negative impact on the global economy, especially since Russia’s invasion of Ukraine last year, on which China has largely sided with Moscow. Balloons either suspected of or confirmed to be Chinese have been spotted over countries from Japan to Costa Rica. Taiwanese media have reported that mysterious white balloons had been spotted over the island at least three times in the past two years. That's especially concerning because China claims Taiwan as its own territory to be brought under its control by force if necessary and routinely sends warships and military aircraft into the island's air defense identification zone and across the middle line of the Taiwan Strait dividing the sides. Taiwan’s Ministry of National Defense has never explicitly linked the balloons to China. However, the recent furor over the Chinese balloon in the US brought attention back to these mysterious sightings. The size of the Chinese balloon in the US, as well as the equipment attached to it, had all drawn intense speculation as to its purpose. Along with Washington, most security experts dismissed Beijing's assertions that the balloon was intended for meteorological rather than spying purposes. But it doesn't look like any weather balloon that Cheng Ming-Dean, head of Taiwan’s Central Weather Bureau, has seen. “In the meteorology world, I haven’t found a person who has seen or heard of a weather balloon that looks like this,” Cheng said. While China has in recent months moderated the abrasive tone of its diplomacy, it is “still pursuing those broader, long-term strategic agendas on the economic, tech and security fronts," said Collin Koh Swee Lean research fellow at the Institute of Defense and Strategic Studies at Singapore's Nanyang Technological University. “In other words, if you cast the change in rhetoric aside, we’re in fact not seeing any real meaningful improvement in the extant China-US relations, which will continue to be dominated by rivalry," Koh said. “And the latest spy balloon incident only looks set to broaden the schism."