MEXICO CITY >> Behind a crumbling brick wall in a working-class neighborhood of Mexico City lurks a seemingly innocuous car lot. But it could be a sign of a potentially grave threat to the North American auto industry.

A makeshift dealership for the Chinese electric vehicle company BYD has sprung up in this dusty lot. Esteban Alegría, an employee, said the dealership was selling cars as fast as they arrived from China. Alegría’s top seller is the Dolphin Mini, a small but capable four-door electric compact that costs about $18,000, about $10,000 less than the cheapest battery-powered vehicle available in the United States.

Alegría’s dealership is one of dozens that Chinese carmakers such as BYD, Chery, Geely and SAIC are opening up around Mexico as they establish a foothold in North America.

Chinese carmakers are effectively barred from the United States by tariffs that double the sticker price of vehicles imported from China, and they are not yet manufacturing significant numbers of vehicles in Mexico that could be exported across the border.

But their ambition to expand overseas is on vivid display in Mexico and across Latin America, Asia, Europe and Africa. Ads for Chinese brands are in airports and soccer stadiums and loom above Mexico City streets on large billboards. Chinese cars, both gasoline and electric models, are an increasingly common sight.

BYD and others are also looking for places to build factories in Mexico, although none have announced firm plans. Initially, the plants would serve Latin America, part of a campaign by Chinese automakers to erode the dominance of Japanese, American and European carmakers in places like Brazil and Thailand.

But there is little doubt that, eventually, Chinese carmakers hope to use Mexico as an on-ramp to the United States.

“Maybe next year BYD can enter the United States,” Alegría said optimistically, as salsa music blared from a speaker hung on a pole and two men washed the dust from a newly arrived Dolphin. Nearby, workers mortared a cinder block wall, part of a new building that will replace the one-room sales office made of rough bricks topped by a corrugated metal roof.“If not,” Alegría added, with a smile, “I can deliver.”

It is very unlikely that the Dolphin or any other Chinese car brand will be available in the United States soon. Because of the high tariffs, Chinese carmakers have not tried to establish dealerships or get approval from federal regulators to sell in the United States. (BYD does make electric buses in California.)

And someone buying a BYD from a Mexican dealer like Alegría would have a hard time registering and insuring it in the United States because the cars have not demonstrated that they meet safety standards.

President Joe Biden and President-elect Donald Trump have been emphatic about wanting to keep Chinese automakers out of the United States, well aware of the threat they pose to U.S. car and auto parts factories that employ 1 million workers.

Trump has threatened 25% tariffs on all Mexican products, including cars. Biden has pursued policies aimed at fending off the challenge from China, including subsidies for U.S. battery factories. The Chinese government has long subsidized carmakers with the goal of becoming a major auto exporter.

But in the years to come it may be difficult to explain to consumers in the United States why they’re not allowed to buy inexpensive electric vehicles that are readily available across the border, especially if they’re made in Mexico, which already manufactures millions of cars for the United States.

Less than 20 years ago, Chinese cars were widely seen as inferior, even by many Chinese drivers. But in recent years, the country’s manufacturers have pulled even with foreign rivals in mechanical quality, analysts say, and often surpass U.S., Japanese and European carmakers in battery technology, autonomous driving and entertainment software. (Think in-car karaoke and rotating touch screens.)

Chinese carmakers have clawed significant market share domestically from once-dominant companies like Volkswagen. Even Tesla, which has a large factory in Shanghai, has lost ground to BYD and other Chinese carmakers. Elon Musk, Tesla’s CEO, will be in a position to influence U.S. auto and China policy after spending more than $250 million to support the Trump campaign and becoming a close adviser to the president-elect.

“Before the pandemic, the rules were set down by the Western carmakers,” said Felipe Munoz, global analyst at JATO Dynamics, a research firm. “Now it’s the opposite.”

Representatives of several Chinese carmakers declined to comment or did not respond to requests for comment. Jorge Vallejo, BYD’s director general for Mexico, agreed to an interview but canceled abruptly as New York Times reporters waited outside his office in Mexico City. The company’s representative declined to reschedule or make other executives available.

China’s car market is the world’s largest by far, and the growing prowess of domestic producers is having far-reaching effects. General Motors said Wednesday that it would take a more than $5 billion hit to its profit as it restructured its operations in China, which have been losing money in recent years.

Mary T. Barra, GM’s chief executive, acknowledged the price pressure from Chinese carmakers during an interview in October. “We’ll continue to look at smart ways to take cost out,” she said, while insisting that the company could still compete with China.