US Treasury Secretary Steven Mnuchin said that he believed Washington and Beijing were nearing the final stage of trade negotiations, moving closer to what he said would be the biggest change in the economic relationship between the countries in 40 years.

“We’re hopeful that we’re getting close to the final round of concluding issues,” he told the media on Saturday on the sidelines of the spring meetings of the International Monetary Fund and World Bank.

Mnuchin again repeated his claim that the biggest obstacle to a trade deal – how to enforce the agreement – is nearly settled, The New York Times reported.

The US has been pushing China to agree to a mechanism that would allow Washington to impose tariffs on Chinese goods if Beijing reneges on certain parts of the deal.

Mnuchin said that the US and China would both have the authority to enforce commitments that are agreed to, indicating the ability for Beijing to exert some control in the future as well.

“We’ve already agreed there’s a big component of this that there will be real enforcement on both sides,” he said, adding “including a detailed enforcement office on both sides with significant resources”.

American officials have also been pressing China to agree not to retaliate against the United States if it reimposes tariffs on Chinese goods.

China has been reluctant to agree to a one-sided enforcement mechanism, viewing it as infringing on its sovereignty and giving Washington too much power over its economy.

Mnuchin however, did not clarify whether the US and China had agreed on an enforcement mechanism that would allow only Washington to respond with tariffs as punishment for violating the deal.

“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 honour our commitments and if we don’t, there should be certain repercussions, and the same way in the other direction.”

The China-US trade war began last year after President Donald Trump imposed tarrifs worth $250 billion following complaints that China was stealing American trade secrets and forcing companies to transfer technology in exchange for access to its market.