Germany is accusing the United States of using "wild west methods" to obtain personal protective equipment.

The claim came after a delivery of face masks destined for Berlin was diverted en route from China.

German media reported on Friday (local time) that hundreds of thousands of masks purchased from manufacturer 3M and intended for Berlin police were diverted to the US as they were being transferred between planes in Thailand.

Berlin officials confirmed that about 200,000 FFP2 masks already paid for by Germany were seized at a Bangkok airport and didn't reach their intended destination. The masks are the equivalent of the US N95 standard.

Andreas Geisel is the interior minister for Berlin state. He says the diversion of the masks is "an act of modern piracy. This is no way to treat trans-Atlantic partners."

"Even in times of global crisis there should be no wild west methods," Geisel said.

He added he wants the German government to demand the United States adhere to international rules.

The US embassy in Berlin didn't immediately comment.

3M REJECTS TRUMP'S CLAIMS

3M said it would work with the US government to boost the availability of its respirator masks in the US under the Defense Production Act, but it rejected suggestions by US President Donald Trump and others that it was helping higher-paying customers elsewhere ahead of sick Americans.

The company said it has worked transparently with the Trump administration since February, increased its capacity to make N95 respirator masks and tried to route them to the areas with the most critical needs.

"The narrative that we are not doing everything we can to maximise delivery of respirators in our home country, nothing could be further from the truth," Mike Roman, 3M's chief executive, said on CNBC.

"We are doing everything we can to maximise our efforts and to fight covid-19 and to support the health care workers here at home in the US," he said.

3M is the world's leading maker of N95 face masks that are sought by medical professionals because they filter out at least 95 per cent of microparticulates. The company makes about 1 billion such masks annually in plants around the world. Since the covid-19 outbreak, it has said it will double production this year to 2 billion.

Trump on Thursday (local time) invoked the Defense Production Act to compel 3M to give priority to the Federal Emergency Management Agency's needs for N95 masks.

He later tweeted: "We hit 3M hard today after seeing what they were doing with their Masks. 'P Act' all the way. Big surprise to many in government as to what they were doing - will have a big price to pay!"

3M expressed concern that Trump's order will force it to cease exporting US-made masks to Canada and Latin America. In some countries, 3M is the only supplier of N95 respirator masks.

The company warned there are "significant humanitarian implications of ceasing respirator supplies to health care workers in Canada and Latin America, where we are a critical supplier of respirators".

It also said that halting exports of N95 masks may lead other countries where it operates to retaliate by doing the same. "If that were to occur, the net number of respirators being made available to the United States would actually decrease," 3M said.

The company said Trump administration officials last weekend asked it to bring more masks from its overseas factories to the US.

Roman said 3M has already begun to do that. For example, China had approved an increase of exports from a 3M factory there and 10 million masks started being shipped this week.

"We've been telling the administration for days and days," Roman said.

He said 3M reacted to the covid-19 crisis before it hit the US by increasing production in China and in other countries that saw the outbreak first.