Chinese firm ZTE has pleaded guilty to violating US sanctions against Iran and has agreed to pay a fine of 892 million dollars (£726 million).
Justice department officials said the company had illegally shipped sensitive US-made equipment to Iran.
Attorney general Jeff Sessions said the corporation "not only violated export controls that keep sensitive American technology out of the hands of hostile regimes like Iran's", but also "lied to federal investigators and even deceived their own counsel and internal investigators about their illegal acts".
According to legal documents, ZTE obtained the banned goods over a six-year period and shipped them to customers in Iran, in the full knowledge that the sales violated US sanctions.
ZTE entered a guilty plea and also settled charges with the US commerce and treasury departments.