WASHINGTON — The Trump administration and China are close to finalizing a modest trade agreement that would suspend tariffs that are set to kick in Sunday, de-escalating their 17-month trade war.

A “deal is close,” said Myron Brilliant, the U.S. Chamber of Commerce’s head of international affairs, who has been briefed by both sides.

Brilliant said the administration has agreed to suspend Trump’s plans to impose tariffs on $160 billion in Chinese imports Sunday and to reduce existing tariffs, though it wasn’t clear by how much.

In return, Beijing would buy more U.S. farm products, increase Americans companies’ access to the Chinese market and tighten protection for intellectual property rights.

The deal awaits final approval from President Donald Trump.

Trump took to Twitter early Thursday to declare: “Getting VERY close to a BIG DEAL with China. They want it, and so do we!”

The president’s comments triggered a daylong rally on Wall Street. The Dow Jones Industrial Average surged 220 points, or 0.8%.

Thursday evening, a senior administration official said a policy announcement regarding China would take place on Friday. The official spoke on condition of anonymity to discuss internal planning.

Earlier Thursday, a spokesman for China’s Ministry of Commerce, Gao Feng, had told reporters that “the economic and trade teams of both sides have maintained close communication.” He offered no additional details.

Beijing had threatened to retaliate if Trump proceeded with plans to raise tariffs on $160 billion of Chinese imports Sunday.

The two sides are negotiating a so-called Phase 1 agreement as part of the effort to resolve their sprawling trade dispute. Still, the truce leaves unsettled the toughest and most complex issues that have divided the two sides.

Three Democratic senators — Minority Leader Charles Schumer of New York, Ron Wyden of Oregon and Sherrod Brown of Ohio — sent a letter to the White House on Thursday, urging Trump to “stand firm” in the negotiations with China. They called on the president to hold out for “commitments from the Chinese government to enact substantive, enforceable and permanent structural reform.”

The administration accuses Beijing of cheating in its drive to achieve global supremacy in such advanced technologies as driver-less cars and artificial intelligence. The administration alleges — and independent analysts generally agree — that China steals technology, forces foreign companies to hand over trade secrets, unfairly subsidizes its own firms and throws up bureaucratic hurdles for foreign rivals.

Beijing rejects the accusations and contends that Washington is simply trying to suppress a rising competitor in international trade.