Han Dong was operating a crane in China's rust belt last August when he heard about a chance to make it big in America.
Local recruiters told him he could make as much as $2,900 a month, or nearly four times the average wage in China — and could even eventually apply for an American green card.
Instead, Mr. Han said, he ended up working on the construction site of a casino on Saipan, part of an American commonwealth in the Pacific Ocean, where federal officials are investigating working conditions at a project managed by Chinese construction firms. An American green card, which would allow him to be employed legally there or anywhere in the United States, no longer appears very likely.
"They tricked us to come here," Mr. Han said of the agents that transported him to Saipan, where he put up scaffolding for 12 hours a day in the tropical heat. Before the fees he paid out to middlemen to get hired, he made only half what he was promised, he said.
The casino project in Saipan, an island about 3,700 miles west of Hawaii, illustrates a challenge for China, even as it throws an unusual look into the issue of undocumented workers on American soil.
For China, high-profile regional construction projects are crucial to programs like President Xi Jinping's "One Belt, One Road." That program, which envisions economic development across the Asia-Pacific region led by China, would expand the country's influence and demonstrate its construction and development know-how even as it provides a potential outlet for Chinese industrial overcapacity. So far, despite the promise of subsidies from China, One Belt, One Road's progress has been slow — and being outed as an exporter of illegal construction workers to an Asia-Pacific neighbor does not help that agenda.
One Chinese contractor at the site, Suzhou Gold Mantis Construction Decoration, ties the project to One Belt, One Road. "The company will use the Saipan project to fully grasp One Belt, One Road," it said in a statement on its website.
For the United States, the Saipan situation comes as President Trump calls for tougher limits on immigrants working illegally. In that regard, the investigation in Saipan carries a twist of irony: The chairman of the company that is building the casino hotel was once a protégé of Mr. Trump's own casinos in Atlantic City.
In late March, after a worker at the project, the Imperial Pacific casino hotel, died from a fall, F.B.I. agents raided the site and discovered hundreds of undocumented Chinese workers. Last month, United States prosecutors filed criminal charges against a number of individuals associated with two big Chinese contractors. Work on the project now faces delays.
Before the labor issues became public, the Saipan casino project had already drawn attention from casino industry analysts.