Fox News host Neil Cavuto late Tuesday slammed President Trump over his feud with Sen. Bob CorkerRobert (Bob) Phillips CorkerHillicon Valley: Experts worry North Korea will retaliate with hacks over summit | FBI works to disrupt Russian botnet | Trump officials look to quell anger over ZTE | Obama makes case for tighter regs on tech Senate GOP sounds alarm over Trump's floated auto tariffs Biden, Corker honored with Freedom House human rights awards MORE (R-Tenn.) and questioned the president's "erratic behavior."

Cavuto spoke directly to the president, telling him he is alienating senators whose support he needs to pass his tax-reform plan.

“Last time I checked, you are the president of the United States, so tweeting out these tacky insults just seems beneath you,” Cavuto said. “You are running out of friends faster than you are running out of time. You might not like Bob Corker, but a lot of senators do, and you need those senators, sir.”

Trump and Corker have been lobbing insults at each other via Twitter over the past few days. Their feud escalated Tuesday, when the president mocked the senator as “Liddle’ Bob Corker.” 

Cavuto suggested that the president’s personal conflicts are “torpedoing” his own tax reform plan.

“It’s not that some of your ideas aren’t sound, they are,” Cavuto said. “It’s that increasingly, this erratic behavior makes me wonder whether you are.”

Cavuto warned Trump that he will soon lose the support of lawmakers, who will get fed up with his behavior.

”Loyalty works both ways,” Cavuto said. “You can’t drain that swamp if all you’re doing is throwing mud.”