A worker checks a medical N95 mask at a mask factory in southwest China's Chongqing, Feb 17, 2020. (WANG QUANCHAO/XINHUA)

BEIJING - Certification standards of medical supplies could vary in different countries and regions, but this should not stem cooperation to fight against the novel coronavirus disease (COVID-19), a foreign ministry spokesperson said Wednesday.

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Spokesperson Hua Chunying made the remarks at a press briefing in response to reports that the US Food and Drug Administration rejected KN95 masks, a Chinese alternative to N95 masks, from entering the United States.

"I'm not aware of the specifics," said Hua, adding that she did not know why the United States made the decision.

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As masks and respirators are in great demand by many countries including China, many Chinese companies are working around the clock to produce these medical supplies, said Hua, adding that while meeting domestic demands, these products will reinforce other countries' fight against COVID-19.