BEIJING (Reuters) – U.S. Treasury Secretary Steven Mnuchin said on Friday he had a “productive working dinner” the previous night in Beijing, as he headed to a state guest house to begin a day of trade talks.

Mnuchin, along with U.S. Trade Representative Robert Lighthizer, is in Beijing for the next round of discussions as the two countries seek to end a bitter trade war.

“We had a very productive working dinner last night, and we are looking forward to meeting today,” Mnuchin told reporters as he left his hotel. He did not elaborate and it was not immediately clear with whom he had eaten on Thursday night.

U.S. President Donald Trump imposed tariffs on $250 billion of Chinese imports last year in a move to force China to change the way it does business with the rest of the world and to pry open more of China’s economy to U.S. companies.

Among Trump’s demands are for Beijing to end practices that Washington alleges result in the systematic theft of U.S. intellectual property and the forced transfer of American technology to Chinese companies.

U.S. companies say they are often pressured into handing over the technological know-how behind their products to Chinese joint venture partners, local officials or regulators as a condition for doing business in China.

The U.S. government says that technology is often subsequently transferred to and used by Chinese competitors.

The issue has proved a tough one for negotiators as U.S. officials say China has previously refused to acknowledge the problem exists to the extent alleged by the United States, making discussing a resolution difficult.

China says it has no technology transfer requirements enshrined in its laws and any such transfers are a result of legitimate transactions.