The Trump administration just issued a proposal to deny Planned Parenthood funding through Title X, the marquee federal program that provides family planning services to low-income women. It's the most concrete step that the administration has taken to limit abortion access since President Trump's inauguration.

In a 312-page filing on Friday afternoon, the Department of Health and Human Services proposed what abortion rights advocates have referred to as a "gag rule." Under the proposal, the agency wrote that "none of the funds appropriated for Title X may be used in programs where abortion is a method of family planning."

If the rule goes into effect, Planned Parenthood would be barred from receiving funding from the federal program. The change would impact any clinic that supports, performs or even refers patients for abortion services. Since Title X was enacted in 1970, its funds have always been prohibited from paying for abortion services.

"Since day one, the Trump administration, along with its anti-abortion and anti-contraception allies, has made it clear that they want to undermine and restrict people's access to family planning care," wrote Kinsey Hasstedt, a Senior Policy Manager at the Guttmacher Institute, in an email to CBS News.

Title X was created to provide affordable reproductive care to women who otherwise couldn't afford it. Last year, more than four million people relied on Title X for health care services, 41 percent of which received services at Planned Parenthood, according to a the health clinic.

Title X funds have never been authorized to pay for abortions, Hasstedt said. Instead, the money is used for wellness exams, STD and HIV screenings, birth control and contraceptive education, according to Planned Parenthood. Anti-abortion rights advocates argue that any money given to Planned Parenthood - even if it's not used for abortions - frees up funding to be used for the procedure.

Kellyanne Conway, an advisor to President Trump, commented on the proposal to reporters on Friday afternoon, saying clinics that provide women's health services should be "physically separate and financially separate" from those that provide abortions.

"When the president says defund Planned Parenthood, it's really to redirect those moneys to the qualified women's health centers," Conway told reporters. She claimed the rule wouldn't impact low-income women's access to medical services because there were "18 to 20 community health clinics that serve women but don't provide abortions for every one Planned Parenthood in the country."

The proposed rule won't be effective until it's been posted in the Federal Register and 60 days have passed, unless courts intervene.

"We fully expect that lawsuits challenging the rule and seeking to stop its implementation will be filed before those 60 days pass," Hasstedt said.