As Turkish troops invaded northeastern Syria and launched airstrikes that reportedly killed at least seven civilians, Sen. Bernie Sanders issued a statement late Wednesday condemning U.S. President Donald Trump's decision to abandon Kurdish forces and pave the way for Turkey's military assault.

"I strongly condemn Trump's reckless decision to abandon our Kurdish allies to their fate at the hands of Turkish President Erdoğan," said Sanders, a 2020 Democratic presidential candidate. "This is not a case of sending American troops there. They are already there and Trump is withdrawing them, giving the Turkish army permission to invade."

"This is not a case of sending American troops there. They are already there and Trump is withdrawing them, giving the Turkish army permission to invade."

—Sen. Bernie Sanders

Trump on Sunday abruptly announced the withdrawal of U.S. forces from northeastern Syria, a decision that was met with outrage and warnings of a deadly Turkish invasion.

On Wednesday, that invasion began as Turkey began bombarding Kurdish targets in Syria, forcing civilians to flee in panic.

The Kurdish-led Syrian Democratic Forces (SDF) warned in a statement Wednesday that Turkey's assault "will spill the blood of thousands of innocent civilians because our border areas are overcrowded."

Sanders said the U.S. president "should not make significant national security decisions impulsively, by tweets after a single phone call," and urged Congress to assert its constitutional authority over foreign policy.

"Kurdish fighters have fought and died in our joint effort to eliminate ISIS," said the Vermont senator. "They should not be abandoned in this way. Congress must assert its important responsibility over foreign policy and serve as a check on our unstable president."

After Turkey launched its assault on Wednesday, Trump issued a tepid statement denouncing the invasion as a "bad idea."

As The Guardian reported late Wednesday, "activists and observers said at least seven civilians had been killed so far."

"There were also early reports of civilian casualties in border towns hit by shelling," according to The Guardian. "Pictures and video shared on social media showed wrecked buildings and bodies in the rubble."