New York Mayor Michael Bloomberg will give $250,000 (£158,000) to women's group Planned Parenthood after a key breast cancer charity cut its grants.
Mr Bloomberg said thousands relied on the group for care, and they should not be denied access to services.
Susan G Komen for the Cure will no longer support breast exams at Planned Parenthood clinics, it said this week.
Komen has faced a growing backlash from being perceived as bowing to pressure from pro-life groups.
Planned Parenthood is one of the most prominent sexual and reproductive health organisation in the US, and is often the target of criticism from those opposed to abortion.
Komen says that it was compelled to stop making grants to Planned Parenthood were stopped because of new funding guidelines.
Mr Bloomberg's donation comes after Planned Parenthood announced it had received online donations totalling $400,000 - from 6,000 individual donors - in the 24 hours since news emerged of the Komen decision.
A family foundation in Texas has also made a similar-sized grant to the group.
'Politically motivated attack'
In his statement announcing his donation, Mr Bloomberg said "hundreds of thousands of women rely on Planned Parenthood for access to care. We should be helping women access that care, not placing barriers in their way."
Planned Parenthood says the Komen Foundation's funding mostly paid for breast exams at local affiliates, providing an estimated 170,000 screenings each year.
The grants totalled $680,000 last year.
On Thursday, 26 US senators signed a letter calling on Komen to reconsider its decision.
"It would be tragic if any woman - let alone thousands of women - lost access to these potentially life-saving screenings because of a politically motivated attack," the letter said.
Komen CEO Nancy Brinker said the decision had nothing to do with political considerations.
"We don't base our decisions on whether one side or the other will be pleased," she said.
Ms Brinker, a former US ambassador to Hungary, founded the charity after her sister, Susan Komen, died of breast cancer.
However, one top Komen Foundation official resigned on Thursday.
Mollie Williams, the former director of community health programs, said in a statement she would not comment on her departure, but added:
"I have dedicated my career to fighting for the rights of the marginalised and underserved. And I believe it would be a mistake for any organisation to bow to political pressure and compromise its mission."