Rep. Seth Moulton Seth MoultonThe Hill's Morning Report - Presented by Facebook - Markey defeats Kennedy; Trump lauds America's enforcers in Wisconsin Moulton fends off primary challenges in Massachusetts Portland: The Pentagon should step up or pipe down MORE (Mass.), a 2020 Democratic presidential hopeful, said he has never seen a "weaker commander in chief" than 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.

"Part of his job is to be commander in chief, and I have never seen a weaker commander in chief in American history," Moulton, a former Marine Corps officer, said Sunday on MSNBC's "Kasie DC."

ADVERTISEMENT

“The way that he cozies up to our enemies and abandons our allies across the globe, insults our own troops, American heroes like John McCain John Sidney McCainThe Memo: Trump's strengths complicate election picture Mark Kelly: Arizona Senate race winner should be sworn in 'promptly' Cindy McCain: Trump allegedly calling war dead 'losers' was 'pretty much' last straw before Biden endorsement MORE, it’s very hard to imagine anyone going into combat that actually trusts this commander in chief."

“One of the first things you learn when you join the military is that you can drop out of a run and they’ll let you try again, you can fail a test and they’ll let you take that test again, but if you lie about anything, you’re gone that afternoon. That’s how important trust is in the military.”

Moulton's comments came in response to tweets from Trump over the weekend in which he dismissed North Korean short-range missile tests and sided with Kim Jong Un Kim Jong UnSatellite images indicate North Korea preparing for massive military parade South Korea warns of underwater missile test launch by North Korea Trump says he didn't share classified information following Woodward book MORE on criticism of former Vice President Joe Biden Joe BidenBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Democratic groups using Bloomberg money to launch M in Spanish language ads in Florida Harris faces pivotal moment with Supreme Court battle MORE, the 2020 Democratic presidential front-runner.

"North Korea fired off some small weapons, which disturbed some of my people, and others, but not me," Trump tweeted. "I have confidence that Chairman Kim will keep his promise to me."

The president also said he "smiled" when Kim referred to Biden as a "low IQ individual."

Trump has frequently been criticized over his praise for Kim.