A US 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.

But Washington is not ready to give up, and has reportedly told Berlin that it will have to limit intelligence sharing with its close NATO ally if it allows Huawei to provide 5G network equipment.

US Ambassador to Germany Richard Grenell wrote in a letter to German economic minister Peter Altmaier that such cooperation would have to be scaled back, The Wall Street Journal reported Monday.

Despite US claims to the contrary, Germany has insisted that there is no evidence Huawei has or will use its gear to engage in espionage. Last week, Berlin released a revised policy to strengthen security measures for networks, but that the standards will not target specific companies.

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 US claims that Huawei posed a risk.

The same official also raised the issue of a recent lawsuit filed by Huawei against the US government, alleging that a ban was unconstitutional for targeting the firm without evidence. In accordance with the law, the official said, any ban would require proof.

While Australia, New Zealand and Japan all issued policies last year to restrict the involvement of Chinese firms in building 5G networks, European countries have not followed suit. The UK has yet to release official determinations on related security policy, but top intelligence officials have already indicated that London will decide against a ban.