Billionaire businessman Donald TrumpDonald John TrumpO’Malley tells Dems not to fear Trump Right way and wrong way Five things to know about the elephant trophies controversy 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 AlexanderAndrew (Lamar) Lamar AlexanderGOP senator: ObamaCare fix could be in funding bill Collins: Pass bipartisan ObamaCare bills before mandate repeal Murkowski: ObamaCare fix not a precondition for tax vote 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.