(WASHINGTON) -- President Donald Trump attacked outgoing Republican Sen. Thom Tillis on Friday, calling him a "RINO" -- an acronym for "Republican in Name Only" -- and a "quitter" as he appeared to acknowledge the ongoing revolt among some in his own party.

"I called him a 'Nitpicker,' always fighting against the Republican Party, and ME, mostly on things that didn't matter," Trump wrote in a social media post.

"Now he can have all the fun he wants for a few months, with some of his RINO friends, screwing the Republican Party. In the end it will only get bigger, and better, and stronger, than ever before!!!" Trump said.

Tillis is among several Republican lawmakers to criticize aspects of Trump's agenda, most recently the creation of a nearly $1.8 billion so-called "Anti-Weaponization Fund" to compensate those who allege they were wrongly targeted under the Biden administration. The fund was created as part of a settlement agreement in President Trump's $10 billion lawsuit against the Internal Revenue Service.

Tillis slammed the fund as the "payout pot for punks." Critics have said that those who committed violence against police, including Jan. 6 rioters, might be eligible for compensation in addition to Trump's political allies.

"These people don't deserve restitution, they -- many of them deserve to be in prison," Tillis said on Thursday. "Some of them deserve the pardon because they were over prosecuted, but this is, I mean, this is just stupid on stilts."

Congressional Republicans on Thursday punted plans to advance a $70 billion immigration bill as Senate Republicans were poised to try to rein in spending for the so-called anti-weaponization fund, as well as Trump's East Wing expansion and White House ballroom construction project.

Several Republicans who Trump has spurned have become the fund's most outspoken critics, including Louisiana Sen. Bill Cassidy. Cassidy lost his primary race last week after Trump endorsed his opponent.

"People are concerned about paying their mortgage or rent, affording groceries and paying for gas, not about putting together a $1.8 billion fund for the President and his allies to pay whomever they wish with no legal precedent or accountability," Cassidy wrote on X.

Trump on Friday suggested that Tillis' choice to not run for reelection was in some part because Trump declined to give him an endorsement.