The administration’s desire to quickly resolve Nafta could give Canada and Mexico more leverage. Trade experts say a Nafta deal seems more likely than it has in months, since the United States sees new urgency to conclude talks and is at least offering different proposals. But the United States does not appear to be ceding much ground. Larger concessions will need to be made to reach a deal, observers say — and those could come in the final moments.

Antonio Ortiz-Mena, a former Mexican diplomat in the United States, said he believed a deal would be possible in the coming weeks if negotiators were prepared to compromise. However, he said, “I think the biggest threat to Nafta is the United States overplaying its hand and not being flexible enough.”

The Nafta provision regarding automobiles has been among the most contentious, given Mr. Trump’s focus on the car industry and its importance to all three nations’ economies.

American negotiators have dropped an earlier demand that half of the value of an automobile be made solely in the United States to qualify for Nafta’s zero tariffs. Instead, they are asking for an unspecified percentage of each vehicle to be made by workers earning at least an average wage rate for the North American industry, to be recalculated each year. According to preliminary calculations, that wage could be approximately $16 to $17 an hour.

However, other parts of the proposal are unchanged, or add layers of rules. In keeping with its earlier proposal, the United States is asking for 85 percent of the value of a car to be made in North America to qualify for Nafta’s benefits, up from 62.5 percent under the current Nafta deal. But it has set up a complex tiered system for other auto parts, for example requiring 85 percent of engines and advanced batteries to be made in North America, as well as 70 percent of monitors, wiring sets and autonomous vehicles parts, and 50 percent of brake pads and spark plugs.

It also requires 70 percent of certain auto parts made of steel and aluminum to be made in North America — a further boon to the American steel and aluminum industry, which the Trump administration has sought to protect.