Democratic presidential candidate Hillary Clinton stands on stage at the Battle Born Battleground First in the West Caucus Dinner on Wednesday in Las Vegas. (John Locher/ AP)

PASADENA, CALIF. -- The political arm of Planned Parenthood will endorse Hillary Clinton in New Hampshire on Sunday, a Clinton campaign official confirmed.

The endorsement marks the first time in the organization's 100-year history that Planned Parenthood Action Fund has endorsed a candidate in a primary. The endorsement was first reported by CBS News.

“Let’s be clear — reproductive rights and health are on the ballot in 2016," said Planned Parenthood president Cecile Richards. “We're proud to endorse Hillary Clinton for President of the United States.

"No other candidate in our nation’s history has demonstrated such a strong commitment to women or such a clear record on behalf of women’s health and rights," she added. "This is about so much more than Planned Parenthood. Health care for an entire generation is at stake.”

Planned Parenthood is one of the nation's leading providers of abortions and reproductive health services. Its early endorsement of Clinton will effectively mobilize supporters -- and millions of dollars -- nationwide for her candidacy.

Richard is expected to officially announce the endorsement at an event on Sunday in Manchester that kicks off the Action Fund's efforts in the 2016 election season.

During a rally in St. Louis, Mo., on Dec. 11, Democratic presidential candidate Hillary Clinton said she will defend Planned Parenthood, along with a number of civil rights. "I will defend a woman's right to choose and I will defend Planned Parenthood," Clinton said to a cheering crowd. (Reuters)

Clinton has vocally said she will defend the organization from what she has characterized as partisan attacks by Republicans in Congress.

"As a lifelong Planned Parenthood supporter, I’m honored to have the endorsement of the Planned Parenthood Action Fund," Clinton said in a statement. "There has never been a more important election when it comes to women’s health and reproductive rights—and Planned Parenthood’s patients, providers, and advocates across the country are a crucial line of defense against the dangerous agenda being advanced by every Republican candidate for president."

The organization has been under fire for months, after a slew of undercover videos alleged that Planned Parenthood had illegally sold fetal tissue, an accusation it has denied.

But Republicans have not relented. This week, the House and Senate -- both controlled by Republicans -- passed legislation to block federal funding for Planned Parenthood and repeal the Affordable Care Act. President Obama is expected to veto the legislation.

"This week was a jarring reminder of what’s at stake in 2016," Clinton added in a statement. "Thankfully, President Obama will exercise his veto power to stop the Republicans from cutting off women, men, and young people from vital health care services at Planned Parenthood—including cancer screenings, well-woman exams, and STI and HIV tests—and taking away health coverage from 18 million people.

"Any of the Republican candidates will proudly sign that bill into law if they win," she added.

Planned Parenthood said it expects to spend more than $20 million supporting its candidates in the 2016 election -- the most ever in one cycle.