U.S. Trade Representative Robert Lighthizer said that time is running out to renegotiate the North America Free Trade Agreement.

“Our time is running very short,” Lighthizer said Monday during a press conference at the end of the seventh round of negotiations in Mexico City.

Progress on updating the agreement has fallen short of expectations, Lighthizer said.

In a briefing with reporters after the conference, Lighthizer said he believes they may only have one month to complete the negotiations.

Lighthizer’s remarks came hours after President Trump said that the U.S. is still considering scrapping the three-nation trade deal altogether if it cannot be improved through negotiations.

“I feel the longer we proceed the more political headwinds we will face,” he said.

Lighthizer pointed out that the presidential election campaign in Mexico will begin next month. In addition, the U.S. mid-term Congressional elections and provincial elections in Canada loom. “All these complicate our work,” he said.

The final days of the negotiations were drawn into the orbit of the recent announcement by President Trump that the U.S. would impose tariffs on steel and aluminum imports. Canada is the largest exporter of aluminum and steel to the U.S. Nearly 90 percent of Canadian steel production is exported to the U.S. Top trump trade adviser Peter Navarro has said that Canada and Mexico would not be exempted from the tariffs.

Representatives from Canada and Mexico have both decried the tariffs. Canada’s top trade official has described the tariff as “unacceptable.”

President Trump on Monday appeared to offer a concession on steel and aluminum as an additional incentive to Canada and Mexico to reach a deal on Nafta. Speaking to the press during an Oval Office meeting, Trump said that exceptions to the tariffs could be included in a new NAFTA deal.

Lighthizer said that the U.S. may be willing to do separate bilateral agreements with Canada and Mexico if the three-nation talks fail. President Trump has said many times that he prefers bilateral agreements to multilateral agreements.