U.S. President Donald Trump and Chinese President Xi Jinping both expressed optimism on Thursday about resolving their bitter trade disputes ahead of a high-stakes meeting planned for the two leaders at the end of November in Argentina.

Trump said on Twitter that trade discussions with China were “moving along nicely” and that he planned to meet with Xi on the sidelines of the G20 leaders summit, after the two had a “very good” phone discussion.

In comments to state media, Xi said he hoped China and the United States would be able to promote a steady and healthy relationship, and that he was willing to meet with Trump in Argentina.

“The two countries’ trade teams should strengthen contact and conduct consultations on issues of concern to both sides, and promote a plan that both can accept to reach a consensus on the China-U.S. trade issue,” Xi said on CCTV state television.

Xi was quoted by CCTV as saying after the call with Trump that the two leaders had hoped to expand bilateral trade cooperation.

Neither leader specified any details of potential progress in their first known direct discussion in several months. Trump administration officials have said that trade talks with China cannot resume until Beijing comes up with specific actions it is willing take to meet U.S. demands for sweeping changes to policies on technology transfers, industrial subsidies and market access.

The two countries already have imposed tariffs on hundreds of billions of dollars of each other’s goods and Trump has threatened to slap tariffs on the remainder of China’s $500 billion-plus exports to the United States if the disputes cannot be resolved.

But Trump struck a more upbeat tone on Twitter after the phone call with Xi.

“Just had a long and very good conversation with President Xi Jinping of China. We talked about many subjects, with a heavy emphasis on Trade,” Trump tweeted. “Those discussions are moving along nicely with meetings being scheduled at the G-20 in Argentina. Also had good discussion on North Korea!”

U.S Lawmakers in Beijing

Earlier on Thursday, Chinese Premier Li Keqiang told a group of visiting U.S. politicians that China and the United States could overcome their differences and get relations back on track if they worked together in a spirit of mutual respect.

China and the United States are locked in an increasingly bitter trade war, and both countries have already placed tariffs on some of each others’ imports.

Meeting a group of Republican lawmakers in Beijing, China’s Li noted the China-U.S. relationship’s “ups and downs” over the past four decades of diplomatic ties.

“We do hope that China and the United States will meet each other halfway and work together in the spirit of mutual respect and equality,” Li told Trump’s fellow Republicans.

U.S. Senator Lamar Alexander of Tennessee told Li that the delegation was there “to show our respect to a great country and a great people,” and that the two countries “are competitors but not adversaries.”

Alexander said he would be discussing trade with Li, though neither of them mentioned the ongoing tariff war in remarks in front of reporters.

Earlier this week, Trump said he thought there would be “a great deal” with China on trade, but warned that he had billions of dollars worth of new tariffs ready to go if a deal did not materialize.

The United States has already imposed tariffs on $250 billion worth of Chinese goods, with duties on $200 billion of the total set to increase to 25 percent from 10 percent on Jan. 1, 2019. China has responded with retaliatory duties on $110 billion worth of U.S. goods.