ZURICH, Switzerland — When Ricardo Guadalupe stepped into the Las Vegas shop of luxury watch brand Hublot earlier this month, something didn't feel right.“Our boutique was half empty,” the chief executive of the LVMH-owned watchmaker said. “We see fewer Chinese traveling to the US We have less traffic.”The restraint of a key group of consumers is the chief concern of executives gathered at the luxury timepiece expo in Basel, Switzerland, this year. Watchmakers say they’re caught in the middle of the US-China trade war — not because either country is slapping tariffs on them, but because the dispute saps growth prospects in the two largest markets. As Chinese consumers travel less and hold back on splurges, growth in Swiss watch exports has been faltering since the middle of last year."The biggest risk and the one that scares most is the US-China trade war because of what's at stake," Julien Tornare, chief executive of LVMH's Zenith, said in an interview. While the "yellow vest" protests in France and Brexit are other threats, he said, they're more localised.China's consumers account for about one-third of luxury spending and as much as two-thirds of growth, but they've turned cautious amid the slowest domestic economic expansion in almost three decades. Richemont, the owner of Cartier and Baume & Mercier, signalled a Chinese slowdown in November, warning that a weakening yuan or the trade conflicts could further weigh on sales.Hublot and ChopardHublot expects sales growth to halve from last year’s 16 percent. Independently owned Chopard, whose timepieces range from some 4,500 francs ($4,500) to more than 200,000 francs, said it won’t quite achieve the high single-digit growth of 2018.“The biggest risk is that the trade war won’t be sorted out well,” Chopard co-president Karl-Friedrich Scheufele said. “You need to feel good, also about the near-term future.”China is still considered the most promising growth market once trade tensions ease. Alibaba CEO Daniel Zhang said in October that Chinese shoppers will probably make up almost half of the global luxury market by 2025. Hublot’s Guadalupe said his brand’s business could quintuple in China in the future.At Breitling, chief executive Georges Kern said that even amid the current tension, it’s not all gloom and doom. Watchmakers came back quickly after the global financial crisis in 2009 through 2011, he said.“Situations like trade wars, Brexit, natural catastrophes per se put the brakes on demand, but it rebounds very quickly,” he said. “The fastest rebound of the Swiss watch industry was after Lehman Brothers. Then came the great years.”By Corinne Gretler; editors: Eric Pfanner and Thomas Mulier.