WASHINGTON — The Trump administration is poised to issue a sweeping rule that makes it easier for small businesses to band together to create health insurance plans that skirt many requirements of the Affordable Care Act, offering lower costs but also fewer benefits.

The final rule is to be unveiled Tuesday, administration officials and congressional aides said.

President Trump has said millions of people could get cheaper coverage from the new “association health plans.” But consumer groups and many state officials are opposed, saying the new plans will siphon healthy people out of the Affordable Care Act marketplace, driving up costs for those who need comprehensive insurance.

The new entities would be exempt from many of the consumer protections mandated by the Affordable Care Act. They may, for example, not have to provide certain “essential health benefits” like mental health care, emergency services, maternity and newborn care and prescription drugs.

As many as 11 million Americans could find coverage under the new health plans, the Labor Department said in drafting the rule, which carries out an executive order signed by Mr. Trump on Oct. 12.