Treasury Secretary Steven Mnuchin said the U.S. and China have agreed on an ‘enforcement mechanism’ for the trade deal.

Creating procedures to enforce the terms of a trade deal has long been considered one of the most difficult challenges of the trade negotiations underway between the U.S. and China. The U.S. has argued that any deal must include a right to impose sanctions, penalties, and tariffs on China if the Asian nation does not fulfill its promises.

“We’ve pretty much agreed on an enforcement mechanism. We’ve agreed that both sides will establish enforcement offices that will deal with the ongoing matters. This is something both sides are taking very seriously,” Mnuchin said in an interview on CNBC Wednesday. “We are really focused on the execution of the documents.”

That implies the talks are much further along than has been reported earlier.

Mnuchin said a Tuesday meeting Chinese Vice Premier Liu He, China’s top trade negotiator, was “very productive.”

Mnuchin also said that there is no longer a deadline for negotiations, something President Donald Trump has said as well. When the trade truce was first agreed to, the president and others said tariffs would rise after 90 days if an agreement was not reached.

“We are hopeful we can do this quickly, but we are not going to set an arbitrary deadline,” Mnuchin said.

Some China critics say that the U.S. should be disengaging its economy from China’s.

“It’s high time that the Trump administration recognizes that there is literally nothing to talk about on the China trade front,” trade expert Alan Tonelson said in February. “The only sensible China policy approach for America is to disengage economically as thoroughly as possible, reinforce ties with more reliable trading partners, and capitalize on its own immense potential for greater self-sufficiency.”

Mnuchin made clear on Wednesday that he wants the U.S. and China to become even more economically entangled.

“If we can complete this agreement, this will be the most significant changes to the economic relationship between the U.S. and China in really the last 40 years. The opening up of the Chinese economy will be tremendous opportunities with structural changes that will benefit U.S. workers and U.S. companies,” Mnuchin said.