Liberals in Congress went on the offensive Tuesday after President Donald Trump climbed aboard Air Force One and left Singapore, the site of his day-long nuclear disarmament summit with Kim Jong-un.

The North Korean dictator has been geopolitically isolated since he took power in late 2011, largely because of his widely condemned human rights record and his nuclear weapons ambitions.

Trump's decision to meet with Kim as an equal in the hope of persuading him to scrap his weapons of mass destruction stunned Democrats on Capitol Hill – especially after he announced that the U.S. would stop holding military exercises off the hermit kingdom's coastline.

'Kim’s gulags, public executions, planned starvation, are legitimized on the world stage,' Connecticut Democratic Sen. Chris Murphy marveled on Twitter.

'U.S. gives up one of our biggest negotiating chips - military exercises. North Korea ends up BACKTRACKING on previous promises on denuclearization. What the hell?' Murphy asked.

Democrats lashed out Tuesday at President Donald Trump's attemps to persuade North Korean dictator Kim Jong-un to abandon his nuclear weapons program, saying the resulting agreement is vague and full of meaningless platitudes, and could weaken the U.S.

House Minority Leader Nancy Pelosi, uncharacteristically, was one of the more mild-tongued Democrats, complaining that Trump 'elevated North Korea to the level of the United States while preserving the regime’s status quo.'

Connecticut Democratic Sen. Chris Murphy vented that Trump's meeting meant 'Kim’s gulags, public executions, planned starvation' have been 'legitimized on the world stage – and exclaimed on Twitter: 'What the hell?'

Tennessee Democratic Rep. Steve Cohen tweeted a response to the president's claim on Tuesday that Kim 'loves his country very much,' writing: 'Loves it so much that he has them impoverished and enslaved except for those he murders. Loves his country?'

In another Twitter post, Cohen wondered aloud: 'Why do I feel this has been one ballyhooed, expensive, bi-lateral con job?'

Florida Republican Sen. Marco Rubio pushed back, saying Democrats hadn't fretted about former president Barack Obama's decision to meet with the Castro regime two years ago.

'I too have concerns about how all this with #NorthKorea will turn out. But I don’t recall all the “experts” criticizing Obama when he met with a brutal dictator in #Cuba who also oversaw a police state & also killed & jailed his opponents. #DoubleStandard,' Rubio, the son of Cuban émigrés, tweeted.

'When Obama did these things, he was described as enlightened,' Rubio continued. 'When Trump does it he is reckless & foolish. 1 yr ago they attacked Trump for leading us towards war, now attack for being too quick for peace.'

Tennessee Democratic Rep. Steve Cohen was among the more colorful anti-Trump liberals on Tuesday

Cohen wondered aloud: 'Why do I feel this has been one ballyhooed, expensive, bi-lateral con job?'

Trump and Kim met as equals in Singapore on Tuesday, a state of affairs that was the ultimate ego-stroke for the North Korean dictator

Still, Democratic Sen. Dianne Feinstein of California protested that Kim is untrustworthy and blamed Trump for ending the longstanding wargames 'with nothing to show in return.'

House Minority Leader Nancy Pelosi complained the president was so eager to be seen cutting a deal that he 'elevated North Korea to the level of the United States while preserving the regime’s status quo. '

She claimed Trump had made concessions to Pyongyang in exchange for 'vague promises,' and failed to guarantee a 'clear and comprehensive pathway to denuclearization and non-proliferation.'

New Jersey Democratic Sen. Bob Menendez blamed Trump for giving 'a free pass to an international pariah who abuses his own people, kills his own relatives, and routinely threatens our national security.'

The agreement the two heads of state signed Tuesday doesn't include fixed timelines or details about the path forward – or how the West will ensure Kim is keeping his promises.

Florida Republican Sen. Marco Rubio scoffed at Democrats' outrage over Trump's summit with the Asian despot, saying no one got overheated when President Barack Obama met with Cuba's oppressive autocrat Raul Castro

Obama and Castro posed for photographs after greeting one another on March 21, 2016 in advance of formal bilateral talks; the president sat with Castro for an exhibition baseball game and later re-established diplomatic relations with the tyrannical regime

'With no commitments from North Korea, this agreement is less of an accomplishment than anything any previous administration ever negotiated with Pyongyang,' Menendez said.

'In exchange for selfies in Singapore, we have undermined our maximum pressure policy and sanctions.'

Virginia Democratic Sen. Mark Warner said in a statement that 'it’s clear that Kim Jong-un walked away from Singapore with exactly what he wanted – the pomp, circumstance and prestige of a meeting with the President of the United States – while making no specific commitments in return.'

A disgusted Hawaii Democratic Sen. Brian Schatz tweeted: 'This is an abdication of American leadership. Just embarrassing.'

Delaware Democratic Sen. Chris Coons forecasted that the Trump White House won't be up to the task of putting Kim's feet to the fire.

A disgusted Hawaii Democratic Sen. Brian Schatz tweeted: 'This is an abdication of American leadership. Just embarrassing'

Trump left Singapore en route to Guam and Pearl Harbor, Hawaii on Tuesday, before arriving back in Washington on Wednesday morning

'For this agreement with North Korea to mean anything, for it to be anything more than a reality TV handshake summit, there’s going to need to be a lot of hard work in the months ahead,' Coons said, 'and I’m concerned that the Trump Administration isn’t prepared to do that hard work.'

Vermont Democratic Sen. Patrick Leahy cautioned that 'so far all we have seen is a photo op coupled with a few broadly worded commitments.'

On NBC's 'Today' program, South Carolina Republican Sen. Lindsey Graham said that 'Kim comes out of this thing bigger,' but also declared Americans 'come out of it stronger too.'

But he insisted – as has Trump – that the final results of negotiations with Pyongyang should be submitted to senators for ratification as a binding treaty.

'Not only do I want to see the details, I want to vote on them,' Graham said.

'I’m hopeful,' he added. 'I think he has convinced Kim Jong Un that he’s better off giving up his nuclear weapons than he is keeping them.'