One of President Donald Trump’s most loyal supporters in the Senate raged against the president’s Sunday night announcement that America will bow out of Syria while Turkey attacks allied Kurds in the region, calling the decision on Monday “shortsighted and irresponsible.”

Appearing on Trump-boosting morning show Fox & Friends, Sen. Lindsey Graham (R-SC) was asked whether he supported the president’s move, prompting the hawkish Republican lawmaker to exclaim, “Absolutely not.”

“If I didn’t see Donald Trump’s name on the tweet, I thought it would be [former President] Obama’s rationale for getting out of Iraq.” he said. “This is gonna lead to ISIS’s reemergence!”

Graham went on to say this was a “big win for ISIS,” claiming that the Kurds in the area will align with Syrian dictator Bashar al-Assad because they’d have no choice due to the United States abandoning them. “So this is a big win for Iran and Assad,” he added.

(During another Fox & Friends segment, co-host Brian Kilmeade criticized the president as well, calling the president’s decision “disastrous” and that it would leave the Kurds to fend for themselves.)

The South Carolina senator then stated that the “Kurds stepped up when nobody else would to fight ISIS,” noting that if we abandon the Kurds at this point, nobody will want to help America in the future in fighting radical Islam. Graham also pushed back on Trump’s claim that ISIS has been eradicated.

“The biggest lie being told by the administration [is] that ISIS is defeated,” he declared. “This impulsive decision by the president has undone all the gains we’ve made, thrown the region into further chaos. Iran is licking their chops. And if I’m an ISIS fighter, I’ve got a second lease on life. So to those who think ISIS has been defeated, you will soon see.”

“I hope I’m making myself clear how shortsighted and irresponsible this decision is, in my view,” Graham concluded.

The GOP lawmaker continued to blast the president’s move on Twitter following his Fox & Friends appearance, saying he doesn’t “believe it is a good idea to outsource the fight against ISIS to Russia, Iran and Turkey.”

“I feel very bad for the Americans and allies who have sacrificed to destroy the ISIS Caliphate because this decision virtually reassures the reemergence of ISIS. So sad. So dangerous,” he wrote in another tweet. “President Trump may be tired of fighting radical Islam. They are NOT tired of fighting us.”

Furthermore, piggybacking off his assertion on Fox & Friends that he would do everything he can to sanction Turkey if they invade Syria, Graham announced that he would “introduce bipartisan sanctions against Turkey if they invade Syria and will call for their suspension from NATO if they attack Kurdish forces who assisted the U.S. in the destruction of the ISIS Caliphate.”

Graham wasn’t alone among Trump’s allies and loyalists to call out the president over his decision to stand aside as Turkey attacks one of America’s most reliable allies in the region. For example, Nikki Haley, former U.S. ambassador to the U.N., said we “must always have the backs of our allies” and leaving the Kurds to “die is a big mistake.” And Rep. Liz Cheney (R-WY), weeks after competing with Sen. Rand Paul (R-KY) for Trump’s affections, called it a “catastrophic mistake” to pull out of Syria, adding that terrorists “thousands of miles away can and will use their safe-havens to launch attacks against America.”

Facing overwhelming criticism from within his own party on the Turkey-Syria decision, Trump tweeted late Monday morning that if Turkey does anything that “I, in my great and unmatched wisdom, consider to be off limits, I will totally destroy and obliterate the Economy of Turkey (I’ve done before!).”