"Tremendous progress" has been made in talks with Chinese President Xi Jinping, Donald Trump said on the summit's second and final day.
"I think truly progress has been made," the US president said, declaring the relationship as "outstanding".
The two men and their staff sat face to face for talks at Mr Trump's Mar-a-Lago retreat in Florida.
Last year Mr Trump said China had "raped the US" and vowed to brand the superpower a currency manipulator.
But at a welcome banquet it was all smiles and the good spirits appeared to continue on Friday as Mr Xi's visit concluded with a working lunch.
On the night of the Chinese president's arrival, a US airstrike on an airbase in Syria was launched in response to a suspected chemical weapons attack.
The attack was made public on Thursday evening just moments after Mr Xi and his wife left the resort following dinner.
Beijing has avoided publicly taking sides on the issue.
Xi likely to be angry - Carrie Gracie, BBC China editor
China's position on Syria is much closer to Russia's than to the US.
And the Chinese government will guess that the timing of the American missile strike was a blunt message that without more robust Chinese help on dismantling Kim Jong-un's nuclear programme, the next target for pre-emptive American military action might be North Korea.
In Chinese protocol, sudden moves disrupting setpiece occasions are avoided wherever possible, and in private, President Xi is likely to be angry that President Trump chose to strike on the very night of his visit.
But in public Mr Xi stuck to his script about the virtues of co-operation while Mr Trump insisted they'd formed an outstanding relationship and made great progress.
As the two presidents went into their final lunch there were no specifics though, and in the aftermath of the US missile strike on Syria, all the big questions which bedevil the US China relationship have been kicked down the road for President Trump's visit to China later this year.
"We have made tremendous progress in our relationship with China," Mr Trump said on Friday, without going into detail.
Mr Xi urged co-operation on trade and invited his host to visit China.
According to a statement on China's foreign ministry website, Mr Xi told Mr Trump: "We have a thousand reasons to get China-US relations right, and not one reason to spoil the China-US relationship."
On Thursday evening, they dined on pan-seared Dover sole and New York strip steak in an ornate candle-lit private dining room decked with red and yellow flowers.
Mr Trump's daughter, Ivanka, and her husband, Jared Kushner, who both work at the White House, were also among guests.
The leaders of the world's two most powerful economies are a study in contrasts - one a softly spoken Communist Party apparatchik and the other a brash Manhattan property tycoon.
During the election campaign, Mr Trump said massive trade deficits and job losses could no longer be tolerated.
But he has so far not followed through on his threat to formally brand China a "currency manipulator", nor to hit Chinese imports with punitive tariffs.
The Republican president's blue-collar supporters hope he can translate his China-bashing election rhetoric into concrete gains for American manufacturing workers.
One of the most urgent issues for the US is nuclear-armed North Korea, which is trying to develop an intercontinental ballistic missile capable of hitting the west coast of the US.
Beijing has so far been chary of isolating its neighbour, fearing its collapse could spawn a refugee crisis and bring the US military to its doorstep.
Some protesters lined the streets on Thursday to voice their opposition to China's policy in the South China Sea.