For weeks, Jay Foreman, a toy company executive, froze all shipments from China, leaving Care Bears and Tonka trucks piled up at Chinese factories, to avoid paying President Trump’s crippling 145 percent tariff.

But as soon as his phone lit up at 4 a.m. on Monday alerting him that Mr. Trump was lowering tariffs on Chinese imports for 90 days, Mr. Foreman, the chief executive of Basic Fun, which is based in Florida, jumped out of bed and called his suppliers, instructing them to start shipping merchandise immediately.

“We’re starting to move everything,” Mr. Foreman said. “We have to call trucking companies in China to schedule pickups at the factories. And we have to book space on these container ships now.”

If other executives follow Mr. Foreman’s lead, a torrent of goods could soon pour into the United States. While logistics experts say global shipping lines and American ports appear capable of handling high volumes over the next three months, they caution that whiplash tariff policies are piling stress onto the companies that transport goods around the world.

“This keeps supply chain partners in limbo about what’s next, and leads to ongoing disruption,” said Rico Luman, senior economist for transport, logistics and automotive at ING Research.

After talks this weekend in Geneva, the Trump administration lowered tariffs on many Chinese imports to 30 percent from 145 percent. China cut its tariffs on American goods to 10 percent from 125 percent. If a deal is not reach in 90 days, the tariffs could go back up, though Mr. Trump said on Monday that they would not rise to 145 percent. Some importers may hold off on ordering from China, hoping for even lower tariffs later.