Trump told Xi at the start of the meeting he hoped they would achieve "something great" on trade for both countries.
Trump has already imposed tariffs on more than US$250 billion in Chinese goods - about half of the total imported into the United States each year - in an attempt to pressure Beijing to change its trade rules.
Mike Starkey offloads soybeans from his combine as he harvests his crops in Brownsburg, Indiana, Sept. 21, 2018.
The United States said Saturday that it agreed in a long-awaited summit with China to suspend new tariffs for 90 days as the two powers seek to end a trade war.
While Mr Xi agreed to buy an unspecified but "very substantial" amount of agricultural, energy, industrial and other products, the White House said.
After 90 days, if there's no progress on structural reform, the USA will raise those tariffs to 25 percent, White House Press Secretary Sarah Huckabee Sanders said in a statement.
"Both parties agree that they will endeavor to have this transaction completed within the next 90 days". President Trump had planned to raise the tariffs on the $200 billion to 25 percent if he couldn't get a deal with Xi. In exchange, the USA wants an immediate start to talks on Trump's biggest complaints about Chinese trade practices: intellectual property theft, non-tariff barriers and cyber theft.
At the same time, US farmers have been hurt by reduced Chinese imports of soybeans and other products.
Xi also agreed to designate the drug fentanyl as a controlled substance, the White House said.
Powell: US economy healthy and rate hikes aren't automatic
The FOMC is likely to link future interest rate decisions more closely to incoming data and then decide on a case-by-case basis. Those increases have raised its benchmark rate to a still-historically-low range of 2 per cent to 2.25 per cent.
Tensions between Washington and Beijing have increased in recent weeks ahead of the high-stakes meeting between Trump and Xi.
"He may not be a friend of mine anymore, but I think he probably respects me", Trump said in September.
"Only with cooperation between us can we serve the interest of both peace and prosperity", Xi said. For more than a year, Trump has raised concerns about the synthetic opioid being sent from China to the United States, which is facing an epidemic of opioid-related deaths.
On the US side, these included advisers such as Kudlow and Treasury Secretary Steven Mnuchin, who are widely seen as wanting to cut a deal, but also hawkish advisers like Peter Navarro and US Trade Representative Robert Lighthizer.
According to Wang, the two presidents "reached important common understandings and the meeting certainly has charted the course for China-U.S. relations in the some time to come".
Trump struck a positive note as he sat across from Xi, despite the US president's earlier threats to impose new tariffs on Chinese imports. In response, China slapped taxes on $110 billion in American goods.
"For the first time ever, the G-20 recognized the WTO is now falling short of meeting its objectives and that it's in need of reform", a USA official, speaking on condition of not being named, told reporters.