Senator Bernie Sanders this week unveiled legislation to reduce the standard workweek in the United States from 40 hours to 32, without a reduction in pay, saying Americans are working longer hours for less pay despite advances in technology and productivity.

The law, if passed, would pare down the workweek over a four-year period, lowering the threshold at which workers would be eligible to receive overtime pay. The 40-hour workweek has stood as the standard in the United States since it became enshrined in federal law in 1940.

In a hearing on Thursday before the Senate Committee on Health, Education, Labor and Pensions on the proposed law, Mr. Sanders, independent of Vermont, said profits from boosts in productivity over the decades had been reaped only by corporate leaders, and not shared with workers.

“The sad reality is that Americans now work more hours than the people of any other wealthy nation,” he said, citing statistics that workers in the United States on average work for hundreds of hours longer each year than their counterparts in Japan, Britain and Germany.

Senator Bill Cassidy, Republican of Louisiana, said at the hearing that such a reduction would hurt employers, ship jobs overseas and cause spikes in consumer prices.

“It would threaten millions of small businesses operating on a razor-thin margin because they are unable to find enough workers,” Mr. Cassidy said.