BANGKOK — Over nearly 60 years and two generations, Chatchai Lertviwatkul’s family business in Thailand was transformed from a manufacturer of leather gloves to a producer of pet food and treats, with a third of its products shipped to the United States from a modest factory on the outskirts of Bangkok.

So when Lertviwatkul learned in April that President Donald Trump wanted to impose a 36% tariff on goods from Thailand, he was stunned. What would that mean for his company, S.I.P. Siam Inter Pacific, and the country’s pet food export industry?

After a decade of rapid growth, Thailand is now the biggest overseas supplier of pet food to the U.S., accounting for more than one-third of all imported cat and dog food.

As Thailand and dozens of other countries near the end of a 90-day rollback of punishing tariffs to negotiate a permanent deal, Lertviwatkul, 52, said the shock had worn off, but the future of the company’s American business remained unclear.

“We need to see how the Thai government will negotiate,” he said, speaking above the hum of a factory making lickable cat treats for a Canadian customer and mint-flavored dog snacks in the shape of a toothbrush. “We need to wait and see,” he added. “There’s nothing much we can do.”

If the July 9 deadline comes and goes with no deal and Thailand’s tariffs return to the 36% rate announced on what Trump called “Liberation Day,” Lertviwatkul, who produces food and treats that American brands sell, said he would temporarily halt supplying U.S. customers. “We need to pause shipping to the U.S. unless something changes,” he said. “Our customers can’t increase the prices that much at retail.”

But, he said, even a 10% “baseline” tariff that Trump has left in place has proved challenging. Any significantly higher rate would force Lertviwatkul to shift the company’s focus to customers in Asia.

Pet food is one of Thailand’s most significant and fastest-growing export industries. The annual value of its pet food exports has nearly doubled in the past five years, to $2.5 billion, according to the Kasikorn Research Center in Bangkok. It has piggybacked on the country’s robust seafood and food processing industry, using fish and meat byproducts for wet food and treats for pets.

The pet food industry started to grow rapidly during the first Trump term, when many companies wanted to diversify operations away from China. When spending on pets spiked during the pandemic, companies added manufacturing capacity in Thailand to meet the surge in demand.

Purina, the pet food subsidiary of Nestlé, invested $150 million in a new factory making cat food in eastern Thailand three years ago. Mars Petcare, the company behind pet food brands like IAMS and Pedigree, expanded one of its Thai manufacturing facilities in 2021.

Zuru, a conglomerate in Hong Kong that makes a range of consumer goods including toys and beauty products, started building a pet food production site on Thailand’s eastern seaboard late last year. The company plans to consolidate all of its manufacturing, including the products it outsources to other firms, in the country. Production is scheduled to start early next year.

Previously, it had worked with pet food manufacturers in China, the U.S. and Europe.