As the U.S. and China steam toward a full-fledged trade war, American casinos across the world could become collateral damage. Since 2012, mainland China has been the largest source of international travel and travel spending, and Beijing has become increasingly adept at harnessing these globetrotters as a form of economic diplomacy, rewarding friends and punishing enemies. Ominously, this trade war approaches amid looming expiration of casino concessions in Macau, three of them controlled by American companies.

“If China’s government likes you politically, it will encourage Chinese to visit,” China Market Research Managing Director Shaun Rein says. His recent book The War for China’s Wallet, examines how China orchestrates state financial, media and commercial instruments plus consumer spending to reward friends and punish enemies. The book explains China’s worldview of hot, warm and cold partners that receive commensurate shares of its growing wallet. Unlike treaty alliances, these relationships are fluid, shifting as policies and leadership change.

The Philippines provide a prime example. When Philippine President Benigno Aquino III took China to international arbitration over competing claims in the South China Sea, China banned Philippine mangoes and discouraged travel there. When Rodrigo Duterte succeeded Aquino in June 2016, saying he would seek cooperation with China over maritime claims and steer the Philippines away from what Rein calls “American hegemony” in the region, the Philippines became a warm partner.

The results have been staggering. Philippine visitor arrivals topped 6 million for the first time in 2017, growing 11% to 6.6 million. Chinese tourist arrivals grew 43% to 968,447, unseating the U.S. as the Philippines’ number two visitor source – that’s not empty symbolism – behind South Korea. In the first quarter of this year, overall arrivals jumped 15% and Chinese arrivals rose 55%. Meanwhile, Philippine gaming revenue rose 14% to a record US$3.28 billion in 2017, and is up again this year.

Cold partner South Korea’s gaming revenue and tourism arrivals cratered due to China’s vocal opposition to deployment of the U.S. THAAD missile system in 2017 following North Korea’s aggressive missile testing. Chinese arrivals to South Korea plummeted 48% last year, representing nearly 4 million lost arrivals, and have fallen another 10% this year.

Conversely, Cambodia has become a hot partner, defending China’s maritime stance inside Southeast Asia’s ASEAN group. The kingdom saw arrivals from China rise nearly 50% last year to a reported 1.2 million. Gaming revenue increased 85% to $926 billion at NagaWorld, the casino in Cambodian capital Phnom Penh controlled by Malaysian billionaire Chen Lip Keong. NagaWorld, which debuted twin tower extension Naga2 in November, has an affiliated airline that works with China’s state owned travel agency to bring tour groups from second tier mainland cities.

China represents the fifth largest visitor source for the U.S. but that’s not where the U.S. is most vulnerable. Along with exporters, U.S. consumer businesses in China and around the world are exposed on the front lines of any trade war. American owned casinos in Macau and other destinations popular with Chinese travelers are particularly vulnerable to Beijing’s wallet diplomacy.

Mainland China accounts for roughly two-thirds of Macau’s visitors and an estimated 90% of gaming revenue. Through Hong Kong listed subsidiaries, Las Vegas Sands, Wynn Resorts and MGM Resorts International each hold gaming concessions in Macau, the world’s casino capital with five times the gambling revenue of Las Vegas. MGM’s concession expires in March 2020 – the other U.S. operators’ concessions stretch to 2022 – and it just opened a US$4 billion resort in the Cotai gaming hub, a property ramping up more slowly than might be expected under those circumstances. Rein sees a more tempting target for Chinese authorities, though.

“The risks for Sheldon Anderson’s Sands casinos are quite high,” he says. “It is quite possible that China will target his casinos specifically because he is a [Donald] Trump crony. It is possible they will ratchet up police surveillance of his Macau properties in order to spread fear among high rollers and even middle class gamblers that they are being checked in on by the authorities. Or they will launch an audit of their books. Either way, a move could be viewed as having plausible deniability that the government cloaks as a crackdown on corruption or tax evasion, as they did against Lotte in China’s battle with South Korea.”

President Xi Jinping’s crackdown on corruption, that authorities said wasn’t aimed at Macau, brought on a 26 month slump reduced casino revenue by 38% or US$17 billion. Two years into a recovery, Macau’s revenue isn’t yet halfway back to where it was. Imagine the damage that could befall a specific business or three that Beijing does target.