The US ambassador to Berlin has sharply criticised German Economy Minister Peter Altmaier for suggesting a parallel between Chinese and US spying.
The row flared up over Germany's decision not to ban Chinese tech giant Huawei from participation in the German 5G mobile phone network.
"There is no moral equivalency between China and the United States and anyone suggesting it ignores history," US Ambassador Richard Grenell said.
Some see Huawei as a security risk.
The US government is urging Western allies to ban Huawei from bidding for 5G contracts, arguing that the firm is too close to the Chinese Communist Party and Chinese intelligence services.
Meanwhile, a new opinion poll suggests a wide gap between the views of Americans and Germans on US-German relations.
Three-quarters of Americans surveyed were positive. But nearly two-thirds of Germans felt relations were bad, the Pew Research Center/Körber-Stiftung poll found.
During a TV debate on Huawei on Sunday, Mr Altmaier recalled the 2013 scandal over US surveillance of Nato allies via the National Security Agency. It emerged that the NSA had even spied on Chancellor Angela Merkel.
Mr Altmaier said that "Germany still did not impose any boycott" on the US despite the NSA scandal.
"The US also demands from its companies that they pass on certain information needed to fight terrorism," he said.
His remark was an apparent riposte to US fears that Huawei, a world leader in new-generation mobile technology, would pass on sensitive data records to the Chinese government.
You need to be able to trust that 5G equipment and software companies will not threaten your national security, privacy, intellectual property, or human rights. Trust cannot exist where telecom vendors are subject to an authoritarian government that lacks an independent judiciary https://t.co/LdO1iwhVms— US-Botschaft Berlin (@usbotschaft) November 25, 2019
China is Germany's biggest trading partner. Yet German intelligence officials have also advised Mrs Merkel's government to bar Huawei from Germany's 5G roll-out.
Ambassador Grenell said equating US government action with that of the Chinese Communist Party was "an insult to the thousands of American troops who help ensure Germany's security and the millions of Americans committed to a strong Western alliance".
"These claims are likewise an insult to the millions of Chinese citizens denied basic freedoms and unjustly imprisoned by the CCP," he added.
Last year Mr Grenell angered Mrs Merkel's centre-left Social Democrat partners by saying he wanted to "empower" Europe's conservatives.
President Donald Trump has chided Germany and other Nato allies who are failing to meet a Nato target for defence spending. Germany, Italy and Spain are well below the 2% of GDP (total national output) target.
In the new opinion poll, conducted in late September in the US and Germany, 85% of Americans surveyed saw the US military bases in Germany as important for US national security. But just 52% of Germans saw them as important for their country's security.
The US has kept a large military presence in Germany - currently 35,000 soldiers - since the end of the Cold War. About 17,000 American and 12,000 German civilians also work for the US military in Germany.