US President Donald Trump has signed a new measure aimed at rolling back federal funding for the US women's health group Planned Parenthood.
The legislation removes an Obama-era rule that prohibited states from withholding funding for family planning services that provide abortions.
A Republican-led Congress passed the measure last month with Vice President Mike Pence casting a tie-breaking vote.
Republicans have long vowed to defund the group over the issue of abortions.
Planned Parenthood, a reproductive health organisation, provides birth control, STD testing, cancer screenings, breast examinations and pregnancy terminations.
Mr Trump signed the legislation privately without media present on Thursday, repealing a rule issued in the final days of Barack Obama's administration.
He signed the resolution under the 1996 Congressional Review Act (CRA), which allows lawmakers to nullify regulations within 60 days of enactment as long as the president agrees.
Republicans have overturned several Obama-era rules using the CRA.
Mr Obama's regulation prevented states from withholding money from a provider for any other reason than an ability to provide family planning service.
That rule was instituted after more than a dozen conservative states denied grants to Planned Parenthood through a Nixon-era family-planning programme known as Title X.
But now state governments will have the latitude to determine how to distribute Title X grants, allowing some conservative states to undercut Planned Parenthood and other abortion groups.
Planned Parenthood receives hundreds of millions of dollars a year in funding from the federal government, but it is banned by law from using any of that money to fund abortions except in cases of rape, incest or life-threatening situations.
Anti-abortion activists hailed the move as returning power to the states while critics argue the measure is part of a "Republican war on women".
"This puts an end to the outgoing gift that Obama gave the Trump administration which was to disallow states from being in charge of its own family planning funds," said Marjorie Dannenfelser, president of the anti-abortion group Susan B Anthony's List.
She added she expects "to see Congress continue its efforts to redirect additional taxpayer funding away from Planned Parenthood".
Planned Parenthood Executive Vice President Dawn Laguens warned the new resolution would deny as many as four million people access to family planning services.
Many Americans who rely on Title X-funded services are low-income, according to the group. In fact, 80% of Title X patients earn incomes below 150% of the federal poverty level.
"People are sick and tired of politicians making it even harder for them to access health care, and this bill is just the latest example," Ms Laguens said.
"We should build on the tremendous progress made in this country with expanded access to birth control, instead of enacting policies that take us backward."
Earlier this year, Republican lawmakers attempted to cut funding for Planned Parenthood through its plan to overhaul the Affordable Care Act, also know as Obamacare.
Congress rejected that measure due to a lack of support.