Filmmaker Rob Reiner slammed President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE on Thursday, claiming he is “aiding and abetting the enemy” in the "War against Isis" and "Cyberwar against Russia."

“Donald Trump is committing Treason against The United States of America,” Reiner tweeted Thursday. “He is aiding and abetting the enemy in The War against Isis and The Cyberwar against Russia."

"He has turned the world’s oldest Democracy into a wholly owned subsidiary of Vladimir Putin. GOP, WAKE UP!” he added.

Donald Trump is committing Treason against The United States of America. He is aiding and abetting the enemy in The War against Isis and The Cyberwar against Russia. He has turned the world’s oldest Democracy into a wholly owned subsidiary of Vladimir Putin. GOP, WAKE UP! — Rob Reiner (@robreiner) December 20, 2018

On Friday, Reiner claimed Trump is "mentally unstable" and accused the president of taking steps to "destroy" U.S. independence.

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"Each day this mentally unstable man takes a step closer to destroying 242 yrs. of self rule. And though Democrats want to be restrained, impeachment is inevitable," he tweeted.

"Then GOP Senators will have to make a choice. Either protect Democracy or continue to enable an ignorant criminal," he added.

Each day this mentally unstable man takes a step closer to destroying 242 yrs. of self rule. And though Democrats want to be restrained, impeachment is inevitable. Then GOP Senators will have to make a choice. Either protect Democracy or continue to enable an ignorant criminal. — Rob Reiner (@robreiner) December 21, 2018

Reiner's comments came one day after Trump declared victory against ISIS in Syria and announced his administration's decision to withdraw troops from the nation.

The announcement drew bipartisan criticism, prompting a group of senators from both parties to send a letter to Trump on Wednesday asking him to reconsider his decision.

“If you decide to follow through with your decision to pull our troops out of Syria, any remnants of ISIS in Syria will surely renew and embolden their efforts in the region," they wrote.

The senators, including Lindsey Graham Lindsey Olin GrahamSenate GOP aims to confirm Trump court pick by Oct. 29: report The Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting Senate GOP sees early Supreme Court vote as political booster shot MORE (R-S.C.), Jeanne Shaheen Cynthia (Jeanne) Jeanne ShaheenSenate Democrats introduce bill to sanction Russians over Taliban bounties Trump-backed candidate wins NH GOP Senate primary to take on Shaheen Democratic senator urges Trump to respond to Russian aggression MORE (D-N.H.), Joni Ernst Joni Kay ErnstThe Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting Liberal super PAC launches ads targeting vulnerable GOP senators over SCOTUS fight Romney backs pre-election Supreme Court vote, paving way for McConnell, Trump MORE (R-Iowa), Angus King Angus KingGovernment watchdog recommends creation of White House cyber director position Democrats step up hardball tactics as Supreme Court fight heats up Shakespeare Theatre Company goes virtual for 'Will on the Hill...or Won't They?' MORE (I-Maine), Tom Cotton Tom Bryant CottonGOP brushes back charges of hypocrisy in Supreme Court fight Trump uses bin Laden raid to attack Biden Battle lines drawn on precedent in Supreme Court fight MORE (R-Ark.) and Marco Rubio Marco Antonio RubioOvernight Defense: Pentagon redirects pandemic funding to defense contractors | US planning for full Afghanistan withdrawal by May | Anti-Trump GOP group puts ads in military papers Democrats step up hardball tactics as Supreme Court fight heats up Press: Notorious RBG vs Notorious GOP MORE (R-Fla.), expressed concern that the decision would bolster Russian influence in the region.

"As you are aware, both Iran and Russia have used the Syrian conflict as a stage to magnify their influence in the region," the senators added. "Any sign of weakness perceived by Iran or Russia will only result in their increased presence in the region and a decrease in the trust of our partners and allies."

Reiner has been a frequent critic of Trump, often taking to Twitter to lambast the president.

Reiner has called for Americans to increase their protests against the president, saying in June that he didn't think there was a "line" that could be crossed when it came to demonstrating against Trump.