President Donald Trump’s trade deal with Canada and Mexico to replace Nafta may not have enough support to win approval in the U.S. Senate, the chamber’s No. 2 Republican said.

“I know people are still going through the details but it’s not a foregone conclusion that it will get confirmation by the Senate,” John Cornyn of Texas told reporters on Tuesday in Washington.

He said the earliest that the Senate could pass the measure would be after the Nov. 6 vote, during the so-called lame duck session before the next congress begins in 2019. But he said it could get a vote in the next congress.

The new agreement makes modest revisions to a trade deal Trump once called a “disaster,” easing uncertainty for companies reliant on tariff-free commerce among the three countries. The 24-year-old North American Free Trade Agreement would be superseded by the U.S.-Mexico-Canada Agreement, or USMCA, covering a region that trades more than $1 trillion annually.

Trump has lauded provisions governing automobiles, raising the portion of their content that must originate within the region to 75 percent, from 62.5 percent, and requiring at least 40 percent of a car to come from workers whose pay averages more than $16 per hour.

Senator Ron Wyden, an Oregon Democrat, warned against considering the pact during the lame duck session.

“The last thing that is needed right now at a time of great public frustration with what’s going on with Washington is ramming this through,” said Wyden, the top Democrat on the Senate Finance Committee.