Billionaire businessman Donald TrumpDonald TrumpIntel Dem: Nunes 'sacrificed the good name' of committee with Trump briefing Report: Trump regrets backing health plan before pushing for tax reform Dem rep: 'We must pause the entire Trump agenda' until Russia investigation complete MORE on Monday fired back at a Republican senator who recently said the mogul has no chance of being president. 

Trump took aim at Sen. Lamar AlexanderLamar AlexanderOvernight Regulation: Trump's Labor nominee hints at updating overtime rule Trump's Labor pick signals support for overtime pay hike Live coverage: Day three of Supreme Court nominee hearing MORE (Tenn.), the chairman of the Senate Republican Conference, who said Sunday that Trump is "famous for being famous" and "not going to be president."

"In all fairness, he's not someone that's exactly at the top of this list," Trump said of Alexander during an interview on Fox News. "He's done very little over the years and he does not seem to be an important player in Washington, unfortunately."

Members of both political parties have questioned the wisdom of the outspoken Trump's flirtations with a presidential bid. But that has not stopped the host of NBC's series "The Apprentice" of testing the waters.

He sent a business adviser to Iowa on Monday to meet with officials ahead of a large gathering of potential GOP candidates in the early primary state.

Trump told Fox he would decide whether he'll run for president before June. If he runs, Trump said he would not seek Alexander's endorsement.