Chinese President Xi Jinping welcomes President Trump during a ceremony at the Great Hall of the People in Beijing on Nov. 8, 2017. (Andrew Harnik/AP)

Top White House officials plan to travel to China next week to try to work through unresolved issues as part of ongoing trade negotiations, a sign that talks are continuing but that a deal remains elusive.

U.S. Trade Representative Robert E. Lighthizer and Treasury Secretary Steven Mnuchin will meet with their Chinese counterparts, a senior administration official said, speaking on the condition of anonymity to discuss undisclosed travel plans.

White House officials had hoped that President Trump would be able to host Chinese President Xi Jinping by the end of this month so that the two countries could announce a formal accord, but talks have bogged down over disagreements about how to enforce a new deal and Trump’s demand for far-reaching changes in China’s state-led economic system.

Now it’s possible that the two leaders will not meet until April or even later. Deadlines keep moving. Trump had originally given Chinese negotiators until March 1 to finalize the terms of the deal, or he threatened to raise tariffs on billions of dollars in imports. But he backed down from that threat several weeks ago, declaring that he thought there was progress and that more time was needed.

“Talks with China are going very well,” Trump told reporters Tuesday, although he didn’t offer specifics.

During the 2016 campaign, Trump attacked the Chinese government, accusing it of using unfair currency and trade rules to rip off U.S. companies and consumers. He said that because the United States imports more goods from China than it exports, it creates an unfair imbalance that must be remedied.

He has placed tariffs on imports of about $250 billion in Chinese goods to try to force Chinese officials to negotiate, and the strategy has worked — last year, Xi agreed to begin formal discussions with Trump on a broad trade deal.

Trump and other White House officials have said they are making progress, particularly in areas related to currency ma­nipu­la­tion and intellectual property theft. They also have said that Chinese leaders agreed to increase purchases of U.S. energy and agricultural products. But they have not released specifics about the pact, making it hard to judge the scope of any deal.

White House officials have said the deal would not need congressional approval.

Asked about the status of the China talks, National Economic Council Director Larry Kudlow said that both countries were trying to work through difficult issues and that the Trump administration was happy to take its time to reach an agreement that Trump likes.

“Patience is a virtue,” Kudlow said on C-SPAN’s “Newsmakers” program.