At a post-G20 summit meeting in Buenos Aires, Mr. Trump agreed not to boost tariffs on $200bn (£157bn) of Chinese goods from 10% to 25% on 1 January.
China will buy a ‘very substantial’ amount of agricultural, industrial and energy products, the US says.
Meanwhile, Beijing says the two sides agreed to open up their markets.
It was the first face-to-face meeting between the two leaders since a trade war erupted earlier this year.
The dispute broke out after Mr. Trump complained China was doing nothing to cut its large surplus in bilateral trade.
At the summit in Argentina's capital earlier on Saturday, the G20 leaders agreed on a joint declaration that notes divisions over trade but does not criticize protectionism.
Mr. Trump and Mr. Xi held a ‘highly successful meeting’, the White House says in a statement.
It says the US tariffs on Chinese goods will remain unchanged for 90 days but warns: “If at the end of this period of time, the parties are unable to reach an agreement, the 10 percent tariffs will be raised to 25 percent.”
The US says China agreed to ‘purchase a not yet agreed upon, but very substantial, amount of agricultural, energy, industrial, and other products from the United States to reduce the trade imbalance between our two countries.’
Both sides also pledged to “immediately begin negotiations on structural changes with respect to forced technology transfer, intellectual property protection, non-tariff barriers, cyber intrusions, and cyber theft”, the White House says.
President Trump said earlier this year he wanted to stop the ‘unfair transfers of American technology and intellectual property to China’.
According to the US, China has also signaled it will allow a tie-up between two major semiconductor manufacturers which Chinese regulators have been blocking.
The White House statement said China was “open to approving the previously unapproved Qualcomm-NXP deal.”
Qualcomm - the world's biggest chipmaker - had abandoned its $44bn bid for Dutch rival NXP Semiconductors after Chinese opposition.
The US also says Beijing agreed to designate Fentanyl as a controlled substance. The opioid - much of it thought to be made in China - is driving a huge rise in drug addiction in the US.
Chinese Foreign Minister Wang Yi told reporters after the talks that “the principal agreement has effectively prevented further expansion of economic friction between the two countries.”
He hailed ‘new space for win-win co-operation’; while Chinese state TV said negotiations would continue.