This 2016 file photo provided by The Xerces Society shows a rusty patched bumblebee in Minnesota. The Fish and Wildlife Service said that it was delaying listing the bee species as endangered, one day before it was to take effect. The listing was to take effect Friday, Feb. 10, 2017. Photo by Associated Press

TRAVERSE CITY, Mich.—The Trump administration on Thursday delayed what would be the first endangered designation for a bee species in the continental U.S., one day before it was to take effect.

The U.S. Fish and Wildlife Service adopted a rule Jan. 11 extending federal protection to the rusty patched bumblebee, one of many types of bees that play a vital role in pollinating crops and wild plants. It once was common across the East Coast and much of the Midwest, but its numbers have plummeted since the late 1990s.

Federal law requires a 30-day waiting period before most new regulations become effective. The addition of the bumblebee to the endangered species list was scheduled for Friday. The listing would require the service to develop a plan for helping the bee recover and provide more habitat.

But in a Federal Register notice, the service announced a postponement until March 21 in keeping with a Trump administration order issued Jan. 20. It imposed a 60-day freeze on regulations that had been published in the register but hadn't taken effect. The delay, according to the White House, was for the purpose of "reviewing questions of fact, law and policy they raise."

Fish and Wildlife Assistant Director Gary Frazer said the move was not expected to impact conservation efforts. The federal agency "is developing a recovery plan to guide efforts to bring this species back to a healthy and secure condition," Frazer said in a statement.

Yet with President Donald Trump pledging to cut back on federal regulations, environmentalists said they feared the bumblebee protection might be doomed.

"The Trump administration has put the rusty patched bumblebee back on the path to extinction," said Rebecca Riley, senior attorney for the Natural Resources Defense Council. "This bee is one of the most critically endangered species in the country and we can save it - but not if the White House stands in the way."

No other pending endangered-species listings are affected by Trump's freeze, said Heather Swift, spokeswoman for the Department of Interior, which includes the Fish and Wildlife Service.

The rusty patched bumblebee has disappeared from about 90 percent of its range in the past 20 years. Scientists say disease, pesticide exposure, habitat loss and climate change are among possible causes. It's among a number of bee species that have suffered steep population declines—along with monarch butterflies, another key pollinator.

The American Farm Bureau Federation opposed listing the bumblebee as endangered, saying it could lead to costly limits on land or chemical use and that private partnerships could more effectively preserve bee habitat.

"We're excited that the administration is taking a second look," said Ryan Yates, the group's director of congressional relations.

Associated Press writer Matthew Brown contributed from Billings, Mont.