The warning by Ambassador Gordon Sondland came after a report in business daily Handelsblatt that the German government wants to avoid excluding products offered by HuaweiTechnologies from the next generation 5G network in Germany.
Huawei, the world's biggest producer of telecoms equipment, faces allegations that its equipment could pose a security risk, which it denies. Yet no supporting evidence has been made public. It maintains that it is a privately owned company with no ties to the Chinese government.
The German telecoms authority and IT authority are now working on guidelines and conditions concerning the security of the network.
July's report identified what it called technical problems which limited security researchers' ability to check internal product codes and concerns about the security of third-party components from a USA supplier.
Huawei has spent decades building a strong presence in scores of markets around the world, including the United Kingdom, helped by reliable hardware and competitive pricing.
A British government oversight panel that monitors Huawei's activities in the United Kingdom warned past year that it can provide only "limited assurance" that its telecoms equipment poses no threat to national security.
'It is a complicated and involved process and will take at least three to five years to see tangible results.
This has sparked fears Huawei could be asked by the Chinese government to incorporate "backdoors" into their equipment that would allow Beijing access, for spying or sabotage purposes.
In a letter to Norman Lamb MP, chair of the science and technology committee, Ryan Ding, an executive from the controversial Chinese technology company, pledged to spend £1.5 billion over five years to address security issues flagged last year.
A number of European nations, including the United Kingdom and Germany, have expressed concern about the use of Huawei equipment in their telecoms infrastructure, however earlier this week, France rejected proposals that would increase checks.
Huawei has said it is willing for its equipment and activities to be supervised by the European Union (EU) as it continues to fend off the threat of restrictions on the use of its kit in 5G networks. She added that "safeguards" were needed to protect data.