President Trump said Friday that the United States and China have reached a limited trade deal, marking the first tangible achievement in the 18-month trade war between the world’s two largest economies.

Speaking in the Oval Office during a meeting with Chinese Vice Premier Liu He, the president said negotiators had reached a “substantial phase one’’ agreement, though details remained to be written down. As part of the partial agreement, the White House agreed not to proceed with plans to increase tariffs next week on $250 billion in Chinese goods from 30 percent from 25 percent.

The partial accord, involving major Chinese purchases of US farm products and US tariff concessions, is intended to pave the way for a more complete bargain between Washington and Beijing. Trump and Chinese President Xi Jinping could meet to finalize such an agreement in Chile at an Asian-Pacific leaders summit in mid-November.


“Both presidents have to own this thing,” said Craig Allen, president of the US-China Business council.

News of a potential deal, which capped two days of talks in Washington, had cheered Wall Street earlier on Friday. Even before the president spoke, the Dow Jones industrial average was up more than 480 points, or 1.8 percent, amid hints that a partial accord was imminent. But the lack of specificity in Trump’s announcement, and his comment that the partial deal could still take weeks to iron out, cooled some of that optimism. The Dow closed up slightly more than 300 points on the day.

‘‘This deal temporarily puts off any further escalation of tensions but does not resolve any of the major underlying sources of frictions between the two countries or mitigate uncertainty about the future of the bilateral economic relationship,’’ said Eswar Prasad, former head of the International Monetary Fund’s China unit.

The protracted US-China trade dispute has unnerved investors, disrupted global supply chains, and featured the most aggressive use of tariffs by a US president since the 1930s. Trump says his ‘‘America First’’ policy is designed to benefit workers who have suffered from decades of globalization and prevent China from supplanting the United States as the world’s top technology power.