The sudden rift between the two top U.S. women's health advocacy groups triggered a furious debate on social media sites between supporters and opponents of abortion rights.

Democratic lawmakers called on Komen to reconsider its move as the organization was thrust into the center of an intractable dispute that some say will hamper its work for years to come. New York Mayor Michael Bloomberg pledged his own money to help Planned Parenthood recoup the lost funds.

Planned Parenthood had received about $700,000 annually from Komen to provide poor women with breast cancer screening, education and access to affordable mammograms.

As the outcry intensified, Komen founder Nancy Brinker took to national television and the Internet to deny the charity's decision was the result of lobbying from anti-abortion groups.

"We will never bow to political pressure," she said in a video posted on the Komen website.

"The scurrilous accusations being hurled at this organization are profoundly hurtful to so many of us," said Brinker, who founded the group following her sister's death in 1980 of breast cancer. "More importantly, they are a dangerous distraction from the work that still remains to be done in ridding the world of breast cancer."

But philanthropy experts said it would be difficult for Komen to convince people it was not playing politics.

"There's a long-term weakening of the Susan G. Komen brand from this decision," said Melissa Berman, chief executive of nonprofit Rockefeller Philanthropy Advisers, which counsels wealthy donors who give more $200 million a year.

"We would see donors reluctant to be involved with a charity whose decision-making gets influenced by short-term pressures and politics because you would always wonder who is really in charge."

The Christian Science Monitor reported that the Komen foundation nevertheless reported a 100 percent increase in donations received during the past two days, although it said no hard numbers were available. Komen representatives could not immediately be reached for comment on the report.

A Dallas-based charity, the Lee and Amy Fikes Foundation, said it was making a $250,000 donation to Planned Parenthood to allow it to continue providing breast-screening services in the absence of Komen's support.

"Our family is saddened that the far right has relentlessly and successfully pressured (Komen) to cut funding for breast screening, referral and education support to low-income women who, until now, have been able to depend on the partnership between Komen and Planned Parenthood for their health," the Fikes Foundation said in a statement.

The Komen foundation, known for its pink ribbon symbol and Race for the Cure fundraisers, has collected more than $1.9 billion for breast cancer research and programs. It has affiliates in more than 100 U.S. cities and 50 countries.

Komen said its decision reflected a move to eliminate duplicate grants and tighten eligibility rules. That includes barring money to groups under investigation by authorities. Planned Parenthood is the subject of a probe by U.S. Rep. Cliff Stearns, a Florida Republican who opposes abortion.

POLITICIZING CHARITY

On Facebook and Twitter, Americans expressed anger that a widely supported cancer charity appeared to have taken sides in the polarizing debate.

"Susan Komen would not give in to bullies or fear. Too bad the foundation bearing her name did," writer Judy Blume, known for her books on girls growing up, said via Twitter. Democrats in the U.S. Senate urged Komen to reconsider.

"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," more than 20 U.S. Democratic senators said in a letter due to be sent later on Thursday.

Activists on both sides of the abortion debate cited evidence of a political shift within Komen.

Abortion rights advocates saw it as part of a turn toward the right. Brinker served as an ambassador to Hungary under President George W. Bush. In 2011, she appointed Republican Karen Handel to a senior policy position with the foundation.

Handel, a former Georgia secretary of state, ran unsuccessfully for state governor in 2010 on a platform that called for defunding Planned Parenthood.

Brinker "is overseeing a fundamental transformation of her organization. It has become a political organization. It is no longer an organization whose mission is to advance women's health," said Terry O'Neill, president of the National Organization for Women.

Jeanne Monahan of the conservative Christian group, Family Research Council, described some of the pressures Komen faced.

"Groups didn't even know there was a formal relationship between Planned Parenthood and Komen until the last few years, and Komen got a lot of negative feedback about that from people who are right to life," she said.

About 15,000 anti-abortion activists sent e-mails to Komen in support of its decision, FRC said.

There were signs of dissent within Komen's ranks. Media reports said the Komen foundation's top public health official, Mollie Williams, had resigned after the decision was made in December. Williams declined to comment on her exit because of a confidentiality agreement with Komen.

"The divide between these two very important organizations saddens me," she said in an email. "I am hopeful their passionate and courageous leaders ... can swiftly resolve this conflict in a manner that benefits the women they both serve."

BLOOMBERG PLEDGE

Planned Parenthood, already barred from using federal funds to provide abortions, has seen the U.S. tax dollars it still receives for family aid to poor women come under intensifying Republican scrutiny in Congress.

"Politics have no place in health care. Breast cancer screening saves lives and hundreds of thousands of women rely on Planned Parenthood for access to care," Bloomberg said in a statement, pledging $250,000 to the group.

Planned Parenthood has also come under attack from lawmakers in several states over the past year, including North Carolina, Indiana and Kansas, who have attempted to block state funding.

In Kansas, some local prosecutors are pressing criminal charges against Planned Parenthood, alleging it failed to maintain paperwork related to the abortions it provided.

Brinker told cable TV news network MSNBC that Planned Parenthood had lost funding partly because existing programs did not meet Komen's new standards. She did not elaborate.

(Additional reporting by Michelle Nichols in New York, Anna Yukhananov in Washington and Corrie MacLaggan in Austin, Texas; Editing by Michele Gershberg and Xavier Briand)

• A Permanent Economic Emergency