Jamieson Greer, the U.S. trade representative, said he expected China to agree to purchase more than $10 billion in U.S. agricultural products, as President Trump prepares to wrap up a high-level summit in Beijing.

In an interview with Bloomberg News on Friday, he said the purchases would span a range of farm products and supplement an existing three-year deal for China to buy 25 million metric tons of soybeans annually.

Mr. Greer confirmed that the United States and China would establish a “Board of Trade” to oversee a tariff reduction on about $30 billion in goods. He said the United States was trying to steer trade with China around “the kinds of things we want to be selling,” including airplanes, soybeans, medical devices and energy.

“You can see us bit by bit building up this strategy,” he said.

Mr. Greer also pointed to Mr. Trump’s prior remarks that China would buy hundreds of Boeing airplanes. In a Fox News interview earlier on Friday, President Trump said that Xi Jinping, China’s top leader, had agreed to order 200 Boeing airplanes. The Chinese government also renewed export licenses for some U.S. slaughterhouses to sell American beef in China.

“We’re already seeing them start to fulfill some of their promises,” Mr. Greer said.

The president, administration officials and more than two dozen chief executives traveled to China for two days of meetings that began on Thursday. That evening, Mr. Trump dined with Mr. Xi in the Great Hall of the People in Beijing. On Friday, the leaders were set to talk face-to-face before Mr. Trump’s departure.

The visit has been closely watched as a pivotal moment for relations between the United States and China, geopolitical rivals bound by one of the world’s most profitable commercial relationships. Many officials, including Mr. Greer, have urged that trade with China focus on less sensitive sectors that would not advance China’s technological or military capabilities.

Mr. Greer did not specify what concessions, if any, the United States had offered in return for the promised purchases. Asked whether the Trump administration would raise tariffs on China in the future, Mr. Greer said that the two sides had agreed that “there is going to be a certain level of tariff,” though he declined to say what that was.

To replace the global tariffs struck down by the Supreme Court in February, the Trump administration has launched two trade investigations, which are expected to result in new tariffs on China and dozens of other countries this summer.

On those investigations, Mr. Greer said, “The Chinese are going to be looking at what we’re doing there compared to agreements we’ve had in the past on certain tariff levels and we’ll just have to try to manage that.”

Mr. Greer said there was a “willingness” on both sides to extend the agreement, ensuring that China continues to supply rare earth exports beyond its October expiration.

He added that recent Chinese regulations allowing the government to penalize foreign companies for moving their supply chains out of China were a “strong concern” for him. “We’re trying to manage differences rather than escalate them,” he said.