Six hundred thousand masks recalled. Defective coronavirus test kits. Countries rejecting outright "Made in China" medical supplies.

These recent headlines have thrown a spanner in the works for China, as it tries to use the pandemic to cast itself as a responsible nation, supplying medical equipment to nations in dire need and fill the global leadership void left by the US.

The donations have been widely covered in its state media, with images of smiling Chinese diplomats in countries such as Myanmar, Serbia and even Italy handing over boxes emblazoned with the Chinese flag and a phrase in the country's language celebrating friendship.

China is one of the world's largest producers of face masks and medical equipment. In early February, deep in the throes of the outbreak, it ramped up mask production. By the end of the month, China was making 116 million masks a day. It also stepped up production of testing kits.

As the virus was brought under control, Beijing eased curbs on the export of medical equipment last month, resulting in protective equipment and test kits finding their way round the world.

But there have been issues with the supplies that are sold: The Netherlands said it was recalling 600,000 face masks that did not fit and whose filters did not work.

Spain said 60,000 test kits it bought did not work, and Turkey complained some it had purchased were inaccurate.

While the Chinese embassy clarified that some of the kits bought by Spain were made by a company that did not have an official licence to sell its products, experts quoted by Chinese nationalist tabloid Global Times blamed Spanish medical staff for not using the kits properly.

China has said it is working to fix the problems.

Still, critics warn that China is using the pandemic to further its influence. The European Union's chief diplomat Josep Borrell called it the "politics of generosity".

"China is aggressively pushing the message that, unlike the US, it is a responsible and reliable partner," he wrote in a blog post. "Armed with facts, we need to defend Europe against its detractors."

This led to Chinese telecommunications behemoth Huawei stopping donations to several countries, including Italy, Poland and the Netherlands.

This, in a way, is indicative of China using its might to push countries into a "trade trap", selling only to friends, said Mr Drew Thompson of the Lee Kuan Yew School of Public Policy. "This is not soft power at work, it's coercion."

The issue boils down to conflict of interest because, often, the local government in charge of regulating safety standards has a stake in the manufacturing companies.

In an editorial on Sunday, the Global Times said the issue of quality has been sensationalised and politicised when foreign governments are unwilling to buy from certain companies fearing state links.

"We believe in the face of quality disputes, calmness is required and both sides shouldn't exaggerate the issues," said the editorial.

"Politicising this kind of dispute could jeopardise cooperation in the virus fight and should be avoided in any case," it added.