US President Donald Trump ditched his trademark anti-China bombast, hailing an "outstanding" relationship with counterpart Xi Jinping at the end of a superpower summit Friday overshadowed by events in Syria.

"We have made tremendous progress in our relationship with China," Trump said effusively at the close of a high-stakes but studiously familiar first meeting between the pair at his Mar-a-Lago resort in Florida.

"I think truly progress has been made," Trump said, declaring his relationship with Xi as "outstanding."

The friendly tone was a far cry from Trump's acerbic campaign denouncements about China's "rape" of the US economy and his vow to punish Beijing with punitive tariffs.

Xi reciprocated Trump's warm words, saying the summit had "uniquely important significance" and thanking Trump for a warm reception.

Beijing's most powerful leader in decades also invited the neophyte US president on a coveted state visit to China later in the year. Trump accepted, with a date yet to be determined.

We "arrived at many common understandings," Xi added, "the most important being deepening our friendship and building a kind of trust."

The bonhomie extended behind closed doors, where the US president's grandson and granddaughter sang a traditional Chinese ballad -- "Jasmine Flower" -- and recited poetry for their honored guests, earning praise from their "very proud" mother Ivanka in a tweet.

"Both the atmosphere and the chemistry between the two leaders was positive, the posture between the two really set the tone," said Secretary of State Rex Tillerson.

"All of us are feeling very good about the results of this summit."

The start of the meeting came on a night of high drama as Trump not only met his nearest peer in economic world power for the first time but also launched his first military strike on a state target.

Trump informed the Chinese leader personally of the strike as the 59 Tomahawk missiles were winding their way to the Shayrat airbase.

Although China is not implicated in the Syrian war, Trump's actions resonate widely, not least in the debate over how to tackle North Korea's nuclear and ballistic missile programs.

China and the United States agree Pyongyang's programs are a serious problem, but have not seen eye-to-eye on how to respond.

"There is a real commitment to work together to see if this cannot be resolved in a peaceful way," said Tillerson.

Trump asked Xi for ideas on how to proceed, but held out the possibility of unilateral action.

"(We) are prepared to chart our own course if this is something China is just unable to coordinate with us," said Tillerson. (AFP)