An Iraq War veteran and Democratic congressman said Donald Trump "has absolutely no idea what it takes to fight ISIS" after the GOP presidential nominee said he was being sarcastic when he called President Obama the terror group's "founder."

"Donald Trump has shown that he lies every single day and then the next day he just tries to claim it was sarcasm," Rep. Seth Moulton, D-Mass., said on CNN's "New Day" on Friday morning.

Moulton, who has endorsed Hillary Clinton, called Trump "completely reckless and unfit to be our commander in chief."

"What happens when he presses the nuclear button, and then the next day says, 'Oh, I'm sorry, I was just being sarcastic?'" Moulton remarked, adding that it is "ridiculous" that Trump is even in the running to be president.

Trump caught flak from both sides of the political aisle this week for suggesting that Obama was the "founder" of the Islamic State, also known as ISIS. Even Mike Pence, Trump's running mate, didn't defend the comments, saying instead Obama's policies "created a vacuum of leadership in which ISIS was created."

Given multiple chances to walk back his comments, Trump instead took to Twitter on Friday morning to say it was "sarcasm."

"[B]ut when Trump claims that America is the founder of ISIS, that's something that ISIS uses against us, that's something that ISIS uses to recruit fighters, recruit terrorists, to attack American troops," Moulton said on CNN.

"It makes the work of our troops harder, and it just shows that Trump has absolutely no idea what it takes to fight ISIS, what it takes to be commander in chief and he certainly has no clue what it means to put your life on the line for our country," he added.