The United States on Monday warned Germany that sensitive communications could be compromised if "untrusted vendors" were used within its 5G telecom infrastructure, according to a Wall Street Journal report.

US Ambassador Richard A. Grenell wrote to German Economy Minister Peter Altmaier on Friday, saying the participation of Huawei or other Chinese equipment vendors in the 5G project would mean the "US won't be able to maintain the same level of cooperation with German security agencies," WSJ reported.