“The new administration isn’t going to force Catholic nuns to provide contraceptives,” said Mark Rienzi, senior counsel at the Becket Fund for Religious Liberty, who represents the Little Sisters of the Poor. “We’ve been on a long, divisive culture war because the last administration decided nuns needed to give out contraceptives.”

The new initiatives came a day after Mr. Sessions changed the Justice Department’s position on a related issue: whether a ban on workplace discrimination on the basis of “sex” in the Civil Rights Act of 1964 encompasses discrimination on the basis of gender identity. The Obama administration had adopted the view that it does cover transgender people, but Mr. Sessions said the department should take the position in court that it does not.

Mr. Sessions’s guidance issued on Friday directs federal agencies to review their regulations with an eye to expanding their protections for religious believers. Conservative religious individuals and organizations have objected for years to nondiscrimination laws that have affected whom they can hire and fire, whom they can serve and how they can operate. The new directive affords them far broader latitude.

In issuing the new directive, Mr. Sessions reinterpreted the Religious Freedom Restoration Act, which was adopted by Congress in 1993 with broad support from across the religious spectrum. It says the government could limit the free exercise of religion only if there was a “compelling” reason, and must do so in the least restrictive way possible.

Among the possible results of the guidance, legal directors at liberal advocacy groups said, religious charities or schools that receive government funding could fire an unmarried employee who becomes pregnant, or an employee who marries a same-sex partner. Religious contractors that administer foster care programs could refuse to place foster children with gay couples, even in states that have nondiscrimination laws.

Houses of worship that have been damaged in hurricanes could receive grants from the Federal Emergency Management Agency to rebuild — even if they are using the taxpayer funds to hire only staff members who share their religious beliefs, rather than making the positions open to all.