U.S. Trade Representative Robert Lighthizer said Wednesday that he will be speaking with a Chinese official before President Donald Trump meets with Chinese President Xi Jinping at the upcoming G-20 summit.

But it's still unclear when the currently stalled trade negotiations between the two economic superpowers will restart, Lighthizer said.

"I have a conversation set up with my counterpart on the telephone in the next day and a half, and then I expect to meet with him with [Treasury Secretary Steven] Mnuchin in Osaka before the president meets" with Xi, Lighthizer testified before the House Ways and Means Committee.

Trump announced in a tweet Tuesday that he would have an "extended meeting" with Xi at the summit, which is scheduled for June 28-29 in Osaka, Japan. Xi confirmed the plans to Chinese state media soon after.

Talks between the U.S. and China on a new trade agreement ground to halt in May amid disagreements between negotiators — including Lighthizer's counterpart, Chinese Vice Premier Liu He. The U.S. alleges China reneged on prior commitments made over the course of the discussions.

"When actual negotiations begin again, I can't say at this point," Lighthizer told the Democrat-led committee.

"We're talking, we're going to meet, and, you know, we have the same objective that you and the other members have. And that is that if we can resolve these issues in a way that improves this relationship, preserves the competitive advantage of the United States, we have an obligation to do that, and hopefully we'll get to that point," he said.

Asked by the committee's ranking member, Rep. Kevin Brady, R-Texas, if the U.S. would be ready to engage with China if they returned to the negotiating table, Lighthizer said, "Absolutely, we are ready to engage."

The U.S. and China have slapped punitive tariffs on hundreds of billions of dollars of imports of each other's goods. In May, Trump hiked tariffs on $200 billion in Chinese imports, and threatened to slap duties on another $300 billion after talks stalled out that month.

Trump said last week that he will also meet with Russian President Vladimir Putin at the G-20 summit. Xi met with Putin earlier in June, and heaped praise on the Russian leader.