President Trump’s tariffs are straining the backbone of the United States economy.

While many larger companies have integrated soaring levies that kicked in last month into their businesses without raising prices for customers, a growing number of smaller businesses are confronting a make-or-break moment. Many small businesses lacked the funds or storage capacity to stockpile goods before Mr. Trump’s tariffs kicked in. They have been reluctant to lift prices because they do not want to drive away customers.

That has made some particularly vulnerable to the recent price shocks, leaving them with deteriorating profit margins and no easy choices. Because small businesses are crucial drivers of employment and growth, their health could have far-reaching implications in an uncertain economy.

“It’s hard to breathe,” said Brandon Mills, the chief executive of Total Promotion Company, a small business in Las Vegas that makes promotional products, custom apparel and merchandise.

Mr. Mills, who imports most of the company’s apparel and printing materials from China, said the swelling cost of tariffs has so eroded his margins on some orders that he often wonders if he would have been better off not fulfilling them.

To help compensate for the higher expenses, he has been reducing other costs. A few months ago, he laid off one of the company’s seven workers, an embroiderer. During a bad stretch when orders were low and cash flow dwindled, he asked his bank to extend a line of credit so he could keep paying the bills.

He has lifted prices on garments and other items, but he is wary of imposing additional costs because he does not want to further depress demand.