WASHINGTON — The Trump administration has taken a step closer to relaxing federal regulations governing the amount of time truck drivers can spend behind the wheel, a move that was long sought by the trucking industry but opposed by safety advocates who warn it could lead to more highway crashes.

The Federal Motor Carrier Safety Administration, an agency of the Transportation Department, issued proposed changes Wednesday to the “hours of service” rules that dictate breaks truckers are required to take, and their time on and off duty.

“It puts a little more power back in the hands of the drivers and motor carriers,” said Raymond Martinez, head of the Federal Motor Carrier Safety Administration. Martinez said the agency listened to drivers and their call for more flexible rules.

But highway safety groups have warned that putting the revisions into place would dangerously weaken the regulations.

The government “is offering flexibility without regard for the fact that these weakened rules could be exploited by the worst actors in the industry,” said Harry Adler, executive director of the Truck Safety Coalition.

There were 4,657 large trucks involved in fatal crashes in 2017, a 10% increase from the year before, according to a May report issued by the agency.

Trade groups that represented truck drivers and motor carriers have pushed for years for less rigid hours of service rules, arguing that the regulations were too rigid and out of step with the daily realities confronting most truckers. They found a supporter in President Donald Trump, who has made rolling back layers of regulatory oversight a priority.

“To me, having the flexibility is huge,” said Terry Button, a hay farmer from upstate New York who owns his truck and has logged about 4 million miles since he started driving in 1976.

The existing regulations limit long-haul truckers to 11 hours of driving time within a 14-hour on-duty window. Drivers must have had 10 consecutive hours off duty before the on-duty clock starts anew. A driver who is going to be driving for more than eight hours must take a 30-minute off-duty break before hitting the eight-hour mark.

Under the proposed revisions, truckers could take a break while they are on duty but not driving. Drivers have complained that long waits for cargo to be loaded or unloaded keep them idle yet they are still required to take an off-duty break.

The administration also is proposing to allow drivers to “pause” the 14-hour driving window for an off-duty break of up to three hours, provided the trucker still takes the 10 consecutive hours off duty at the end of the work shift.

Short-haul drivers are exempt from logging their time electronically if they meet certain criteria that include starting and returning to the same location within 12 consecutive hours and not exceeding a 100-mile radius. The proposal would extend the on-duty period to 14 hours and extend the distance limit to 150 miles.

Eric Teoh, a senior statistician with the Insurance Institute for Highway Safety, had urged against lengthening the short-haul work period. In a letter sent to Martinez and the agency last year, Teoh said that a recent Institute study showed that interstate truck drivers operating under the short-haul exemption had a crash risk 383% higher than those not using the exemption.

The American Trucking Associations, whose members include the nation’s largest motor carriers and truck manufacturing companies, said the revisions maintain the “core principles” of the regulations.

A group representing independent truck drivers hailed the “common-sense approach” that will make it easier for truckers to avoid heavy traffic, bad weather and other adverse situations.

The proposal will be published in the Federal Register next and be open for public comment for 45 days.