For good measure, Trump again called Xi a close friend and thanked him for China's role in strengthening sanctions against North Korea.
Xi's presence hung over yesterday's talks: China's leader met twice with Kim in recent weeks and an Air China Ltd jet ferried the North Korean ruler to Singapore from Pyongyang on June 10 ahead of the summit.
Trump's diplomacy "sends all the wrong messages to China, North Korea and Russia," said Malcolm Davis, a senior analyst at the Australian Strategic Policy Institute. "If the US is prepared to make this promise to a brutal dictator, then how trustworthy is he going to be in maintaining a security commitment to his allies?"
Xi's pre-summit meetings with Kim helped restore ties that had been frosty since both leaders took power around the same time about six years ago. The neighbours, which fought together during the Korean War, had grown apart last year after China backed United Nations sanctions crimping North Korea's energy imports and sources of foreign cash to pressure it to halt its nuclear and missile tests.
Japan, the chief US ally in the region, got none of what it wanted - Kim made no promise to address the issue of Japanese citizens abducted by North Korea, and he offered no limits on his ballistic missile programmes. Neither the US nor the South Korean Government would confirm that the Trump Administration warned President Moon Jae In ahead of time about the decision to suspend exercises.
"We will be stopping the war games, which will save us a tremendous amount of money," Trump said during a post-summit news conference. He even adopted North Korea's language for the exercises, calling them "very provocative."
Trump's upside-down calculus, which allowed strategic adversaries China and North Korea to gain at the expense of steadfast allies, echoed the tussle that erupted at last week's Group of Seven meetings in Quebec.
Following the G7, he backed out of a joint communique signed by the six other members, and insulted Canadian Prime Minister Justin Trudeau as "weak" and "dishonest" for criticising US tariffs.
With the summit over, it now falls to US Secretary of State Mike Pompeo to assuage any concerns Japanese and South Korean leaders have with what happened. Pompeo flies to Seoul today for meetings with his South Korean and Japanese counterparts before heading to Beijing for a few hours to do the same with Chinese leaders.
Trump has said repeatedly that the summit was only the start of a process and that the US would not ease up pressure on the North - including a crippling sanctions regime - until its goal of North Korea's "complete, verifiable, irreversible denuclearisation" is reached.
But that language wasn't mentioned in a joint declaration signed by Trump and Kim, and no timetable was set for North Korea to eventually give up nuclear weapons.
That marked a significant walk-back from previous statements by US officials, who had said they wanted a quick process and a significant show of good will from the North.
South Korea appeared to have been blindsided by Trump's change of heart on war games. US officials couldn't confirm that Trump had told counterparts in Seoul about the plan to suspend military exercises, which North Korea has long regarded as a threat.
A spokesman with Moon's office, who asked not to be identified to discuss internal deliberations, said the Government was still trying to understand Trump's "exact meaning or intentions" with the military freeze.
At the same time, the spokesman didn't condemn the decision, and Seoul has repeatedly pressed for a cautious approach to North Korea rather than the hasty agreement that Trump and Pompeo had originally pursued.
"If the goal is to begin to unravel the US-Japan and US-South Korea alliances, then this is the way to launch the process," said Evans Revere, a former US diplomat in South Korea.
"The US has yielded major concessions - the summit itself and the end of our defensive military exercises - in return for what appears to be a vague and undefined premise from the North Korean leader."
Trump rejected the idea that the US was the loser in the talks. "We haven't given up anything," he said. "The meeting was every bit as good for the US as for North Korea."
China was effusive about the talks, with Foreign Minister Wang Yi saying the two sides were "creating a new history." He spoke before Trump and Wang announced the US was suspending the military drills.
"China of course welcomes and supports this," Wang said of the talks. "Because this is the goal we have hoped for and have been working for."
While China opposes North Korea's nuclear weapons, it also wants to prevent a collapse of Kim's regime or war on the Korean Peninsula. Any instability - or alternatively, a deal that leads to a US-aligned unified Korea - potentially could put American troops on its border.
In China, Pompeo's biggest task will almost certainly be to make sure the Government holds up its end of the bargain enforcing the sanctions regime which the US bolstered in recent months and which Trump credits for bringing Kim to the negotiating table.
But soon after the announcement, China was already hinting at the prospect of sanctions relief. Foreign Ministry spokesman Geng Shuang said that sanctions should be revisited if North Korea complies with Security Council demands for denuclearisation.
"Sanctions are a means, not an end," Geng said. "We believe the Security Council should make efforts to support the current diplomatic efforts."
- Bloomberg