Billionaire businessman Guo Wengui speaks during an interview in New York City, April 30, 2017.

Casino tycoon Steve Wynn may have played a central role in a U.S.-Chinese diplomatic episode strange enough that the Wall Street Journal wrote it was "worthy of a spy thriller."

The billionaire CEO of Wynn Resorts, who maintains substantial holdings in the Chinese region of Macau, hand-delivered a letter to President Donald Trump written by the Chinese government, the Journal reported. The letter urged the president to return Guo Wengui, a Chinese businessman who fled the country in 2014 and is now seeking asylum in the United States.

Wynn is the Republican National Committee finance chairman.

The White House and Wynn did not respond to requests for comment from CNBC. Wynn resorts told the Journal the report was false.

Wynn's China properties account for a significant share of his business. Those properties include the Wynn Macau and the Wynn Palace, a $4.1 billion gambling giant that opened in Macau in 2016.

Macau is a so-called "special administrative region" of China that operates with some legal autonomy, according to an agreement signed by China and Macau in 1999. It's one of the world's gambling capitals, and gaming taxes account for more than three quarters of the region's tax revenues.

Both properties are operated on land leased under multi-decade agreements from the government. The casinos are subject to a license renewal process that takes place once a year, according to the company's SEC filings.

The Wynn Palace has been a successful venture for the company.

Earlier this month Deutsche Bank analysts raised their price target for Wynn Resorts after the casino posted results that beat expectations. J.P. Morgan upped its earnings estimates for the property Oct. 5, saying the casino was benefitting from a substantial VIP presence.

In 2016, the Macau properties accounted for more than 60 percent of the company's net revenues, according to the company.