“If complaints are real, we may have to use tariffs to deal with them, and we’re asking the Chinese not to retaliate,” Larry Kudlow, the director of the National Economic Council, told the Fox Business Network in March when discussing enforcement of a deal.

People who have been closely tracking the talks cautioned that enforcement continued to be an obstacle that remained unsettled because China and the United States had not agreed on the specifics of penalties.

“The problem with the so-called enforcement issue has to do with finding a mechanism that allows punishment for violations of the agreement,” said Michael Pillsbury, a China scholar at the Hudson Institute who advises the Trump administration. “That hasn’t been done yet.”

On Saturday, Mr. Mnuchin would not clarify whether the United States and China had agreed on an enforcement mechanism that would allow only Washington to respond with tariffs as punishment for violating the deal.

“I want to be careful in answering that because I don’t want to get into the details of the negotiations and specifically on tariffs,” he said.

But Mr. Mnuchin said that he expected enforcement of the trade pact to be reciprocal.

“There are certain commitments that the United States is making in this agreement and there are certain commitments that China is making, and I would expect that the enforcement agreement works in both directions,” he said. “We expect to honor our commitments and if we don’t, there should be certain repercussions, and the same way in the other direction.”

Mr. Mnuchin would not specify what commitments the United States was making. Mr. Trump has been pushing China to open its economy and end practices that he says have put American companies at a disadvantage.