The nation’s top public health agency in the United States said Friday that in-person or face-to-face schooling can resume safely with masks, social distancing and other strategies, and vaccination of teachers, while important, is not a prerequisite for reopening.

The Centers for Disease Control and Prevention released its long-awaited road map for getting students back to classrooms in the middle of a pandemic that has killed nearly 480,000 people in the US. But the agency’s guidance is just that — it cannot force schools to reopen, and CDC officials were careful to say they are not calling for a mandate that all US schools be reopened.

Officials said there is strong evidence now that schools can reopen, especially at lower grade levels.

Recommended measures include hand washing, disinfection of school facilities, diagnostic testing and contact tracing to find new infections and separate infected people from others in a school. It’s also more emphatic than past guidance on the need to wear masks in school.

“We know that most clusters in the school setting have occurred when there are breaches in mask wearing,” Dr. Rochelle Walensky, the CDC’s director, said in a call with reporters.

The guidance was issued as President Joe Biden faces increasing pressure to deliver on his promise to get the majority of K-8 schools back to in-person teaching by the end of his first 100 days in office. He acknowledged that the goal was ambitious, but added, “It is also a goal we can meet if we follow the science.”

Biden said schools will need more money to meet the CDC’s standards and called on Congress to pass his coronavirus package quickly to get $130 billion in aid to schools.

“We have sacrificed so much in the last year,” Biden said in a statement. “But science tells us that if we support our children, educators and communities with the resources they need, we can get kids back to school safely in more parts of the country sooner.”