U.S. Trade Representative Robert Lighthizer won’t conclude Chinese trade negotiations without substantive changes to intellectual property issues, Republican Senator Rob Portman said in Bloomberg Television interview.

Lighthizer is a “tough negotiator” who is willing to keep the option of increasing Chinese tariffs on the table, Portman said Wednesday. “The Chinese government realizes that. They know they have to come through with something that is more equitable, more fair.”

President Donald Trump is scheduled to meet with Republican members of the Senate on trade issues Wednesday. Lighthizer, Trump’s top trade negotiator, told a Senate Finance Committee hearing Tuesday that the U.S. must keep open the option of raising tariffs on Chinese imports as a way to ensure Beijing lives up to a trade agreement that could be finalized in a matter of weeks.

The U.S. is in a “pretty good position” in talks with China right now, said Portman, himself a former U.S. Trade Representative. He said the next meeting will be between Trump and Chinese President Xi Jinping and “they won’t meet unless there’s something positive to report.”

Lighthizer told Senate Finance Committee members that he couldn’t predict success yet on Chinese trade talks but that negotiators are “working hard” and have “made real progress.”

Separately, Portman said he expects Congress will approve the new U.S.-Mexico-Canada trade agreement negotiated by the Trump administration last year. The agreement is “positive” for Democrats, Portman said, because “there were no environmental or labor standards” under the existing North American Free Trade Agreement.

“This is a lot better than the status quo,” Portman said. The U.S. must negotiate on steel and aluminum tariffs because Mexico and Canada will have tough time ratifying the agreement until those areas are resolved, according to Portman, who added that he plans to raise this issue with the president.