An embassy spokesman declined to comment specifically on a Wall Street Journal report about the U.S. government's first explicit warning to Germany of consequences if China's Huawei Technologies Co gets a role in Germany's next-generation mobile infrastructure.
The US has been using its clout to try and persuade other countries that it should boycott the company as it has done. [Grenell] noted that the code running on 5G equipment would need frequent updates and was so complex that the potential for so-called backdoors and other system vulnerabilities couldn't be ruled out even if Huawei were to let regulators regularly inspect its software.
Altmaier apparently received the US letter on Friday - one day after he said Germany doesn't want to put an outright ban on Huawei.
The US security agency underscored that the US would not deny all intelligence from Germany in case the latter would go in bed with Huawei.
The warning came in a recent letter from the USA ambassador to Germany seen by the Wall Street Journal.
While the U.S. embassy in Berlin would not confirm that a message was sent, the German Federal Economics Ministry did tell the Frankfurter Allgemeine Zeitung (FAZ - auf deutsch) that the letter had been received and would be "answered promptly". "There will be a quick reply".
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A Labour Party spokesman said: "Allowing a free vote on no deal shows Theresa May has given up any pretence of leading the country".
The German Economy Ministry confirmed that the letter had been received.
A United States campaign to scare European allies away from using Chinese telecommunications equipment went up in flames over the past several months, most recently evidenced by Germany's decision last week not to ban the gear from its next-generation wireless network.
"An official from the German Economic Ministry dismissed the letter from Grenell, saying that it included no new information and reiterating that there was no evidence to support USA claims that Huawei posed a risk", Asia Times reported on Monday.
Tensions have also run high over the detention of Huawei chief financial officer Meng Wanzhou, who is facing possible extradition to the US on allegations she committed financial fraud in the course of allegedly violating worldwide sanctions on Iran.
Essentially, the lawsuit is daring USA intelligence services to put up or shut up.