Almost unnoticed in the wars over the federal budget has been a pitched battle over money for Planned Parenthood, which provides contraception, medical services and abortions at 800 clinics around the country.

For the last several weeks, those on opposite sides of a sharp cultural divide have engaged in dueling rallies, virtual conferences, online petitions and phone banks as crucial Congressional votes drew near. At stake is more than $75 million that Planned Parenthood receives to provide family planning assistance to low-income women, money that its opponents say only frees up funds for abortions.

Now, in a surprise step that has set off deep alarm among advocates for women’s health, the newly conservative House of Representatives has proposed cutting the entire $317 million program of aid for family planning, known as Title X, in a 2011 spending bill that is expected to pass by the weekend. A proposed amendment to the bill would also bar Planned Parenthood from receiving any federal funds for any purpose. The amendment was the subject of an emotional three-hour debate on Thursday night.

The fight will shift to the Senate, where the Democrats retain a small majority. It is unlikely they will agree to cut all financing for Planned Parenthood, let alone the broader federal aid for contraception that serves five million low-income women, said Susan Cohen, director of governmental affairs for the Guttmacher Institute, a research organization. But more legislation in the House aimed at Planned Parenthood is in the offing, putting the organization in its most precarious political spot in decades.