This undated file photo shows the national flags of China (left) and the United States. (PHOTO / XINHUA)

China on Friday urged the United States to earnestly respect international law and refrain from political manipulation after Washington called for "sharper rules" for unknown aerial objects.

"The US is not qualified to talk about establishing so-called common global rules but should earnestly abide by international law and international customary practice," said Foreign Ministry spokesman Wang Wenbin.

His remarks came after US President Joe Biden said on Thursday that Washington is developing "sharper rules" to track, monitor and potentially shoot down unknown aerial objects.

China has made it clear that the entry of a Chinese unmanned airship into US airspace was an unexpected and isolated incident which also tests US sincerity and its ability to properly manage crises and stabilize Sino-US relations

"There are already relevant international legal norms on civil aircraft in international practice," Wang said at a daily news briefing, accusing the US of overreacting and violating international law after recently shooting down a Chinese unmanned airship of a civilian nature.

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The US also released several high-altitude balloons from its soil, illegally flying them over Chinese airspace multiple times without Beijing's approval, Wang added.

China has made it clear that the entry of a Chinese unmanned airship into US airspace was an unexpected and isolated incident which also tests US sincerity and its ability to properly manage crises and stabilize Sino-US relations.

Wang dismissed the remarks of Karine Jean-Pierre, the White House press secretary, on Thursday that China flying its "surveillance balloon" into US airspace was "irresponsible", and she said Beijing wanted to deflect intention and try to put its spin on the incident.

"The US should not exploit the incident to engage in political manipulation, smearing and attacking China," Wang said.

Speaking of US double standards, Wang asked: "Why can the US see balloons flying at 18,000 meters above the ground but turn a blind eye to toxic mushroom clouds involving vinyl chloride, a highly toxic chemical, over (the state of) Ohio?"

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Wang questioned why Washington called for holding perpetrators accountable immediately after the blast of the Nord Stream gas pipeline, but remained "unusually silent" following the release of a report by Seymour Hersh, a US investigative journalist.

Wang also called for the US to explain what three high-altitude objects recently shot down were, saying, "If the US does not consider the appearance of these objects in its airspace as irresponsible acts, how can it make unwarranted accusations against China?"