Prominent American journalist Tucker Carlson claimed the CIA read his text messages sent before the war with Iran in an attempt to portray him as a foreign agent.

The 56-year-old Carlson said the US Justice Department is preparing to charge him with being an unregistered foreign agent of Iran on the CIA's recommendation, in a video published Saturday evening.

"The CIA is preparing some kind of criminal case against me, a crime report to the Justice Department based on an alleged crime that I committed," the journalist said in the video.

"What is that crime? Well, I was talking to people in Iran before the war. They [the CIA] were reading my messages," he added.

Carlson also claimed he would be charged under the Foreign Agents Registration Act (1938), which requires anyone paid by foreign governments for lobbying or political propaganda to register with the Justice Department.

The journalist denied the accusations against him. "I am not an agent of a foreign power. Unlike many people commenting on US policy and world affairs, I am loyal only to the United States and have never acted against it," he said, adding that he has "never taken money" from another country.

"My job is to constantly talk to everyone and try to figure out what is happening in the world. I am an American. I can talk to anyone," he added.