The Republican head of the U.S. Senate Judiciary Committee said on Sunday he plans to ask the FBI about a report it launched a probe into whether President Donald Trump has been working on Russia's behalf, suggesting the agency may have gone too far.

"I am going to ask the FBI director — was there a counterintelligence investigation opened up regarding the president as being a potential agent of the Russians? I find it astonishing," Sen.Lindsey Graham said on the "Fox News Sunday" program.

"If this really did happen, Congress needs to know about it," he added. "How could the FBI do that? What kinds of checks and balances are there?"