Harry Hausler was speaking at an event a few months ago in Khayelitsha, a Cape Town township, where he ran into several people he knew but hadn't seen in years.

Hausler, a family physician, had first met them back around 2007, a period when people living with AIDS in South Africa could not count on getting access to life-saving treatment. These patients were "really emaciated" at that time, says Hausler. "Their immune systems were completely depleted."

When Hausler saw them 16 years later, they were in very different shape.

"They'd started antiretroviral treatment, rebounded, gained their strength and their weight back and subsequently had long and happy lives," he says. "Some of them have had children who have been born HIV-negative because the mothers were on antiretroviral treatment, so they didn't transmit the virus to their children. And some of those children are now graduating from university in South Africa!"

Hausler, who these days is CEO of the organization TB HIV Care, has little doubt what turned life around for these and millions of other people.

"It's really incredible what difference PEPFAR has made in South Africa."

PEPFAR, the President's Emergency Plan for AIDS Relief, has funded antiretroviral treatment for more than 20 million people across more than 50 countries in its two decades of existence. It's a rare example of bipartisan politics – launched by President George W. Bush in 2003 and supported by both parties, It's considered one of the most successful and broadly supported aid programs in American history.

And yet, Congress appears poised to let the program's authorization lapse on Oct. 1. That wouldn't put PEPFAR out of business, as the program is permanently enshrined in the law. But it's the first sign of uncertainty in support for this bedrock program credited with saving some 25 million lives worldwide. And critics are making bold and controversial assertions. "Biden has hijacked PEPFAR to promote abortion," was the headline of a press release issued on Thursday by Rep. Chris Smith, R-N.J.

So what would happen if the deadline comes and Congress does not re-authorize?

A handful of requirements on PEPFAR spending would be lifted – such as dedicating 10% of funds to serving orphans. Funding would move to an annual appropriation rather than a five-year cycle. In 2023 PEPFAR received $6.9 billion.

Partner groups in Africa worry that such a move would amount to backpedaling on an initiative that has made major strides against AIDS.

What critics of PEPFAR are saying

The complaints about PEPFAR center on the Biden administration's lifting of the so-called "Mexico City Policy." That policy prohibited U.S. foreign aid from flowing to organizations that – with funds raised from their own, non-U.S. government sources – provide abortions, referrals and information on abortion or advocate for abortion services. (U.S. law has long prohibited foreign aid money from being used to provide abortions.)

The Mexico City policy was first instituted by President Ronald Reagan through executive action. It has been rescinded by each successive Democratic administration and restored by each Republican. However, until President Trump, it had only been applied to family planning programs. Trump was the first president to extend it to PEPFAR.

Biden's move to rescind the policy put PEPFAR in the sights of Evangelical Christian groups and other abortion opponents. They say that even though the U.S. program does not directly fund abortions, money is fungible. Organizations could shift other funds to family planning services, providing indirect U.S. taxpayer support for abortion.

"There's a concern about using U.S. tax dollars to prop up and bolster these organizations, given their own stated mission of promoting and performing abortion in Africa," says Travis Weber, vice president for policy and government affairs at the Family Research Council, a Christian think tank that strongly opposes abortion. Weber cites groups such as Population Services International, whose PEPFAR-funded activities are separate from its broader reproductive health care services, which include abortions.

"Our position is, if they just attach the Mexico City policy to [PEPFAR], we're fine," Weber says. "It could get done tomorrow. There's just a lack of willingness to do that. I understand that hasn't been done by other Democrat administrations, but that doesn't mean it can't be done in the future."

PEPFAR skeptics also include The Heritage Foundation, Susan B. Anthony Pro-Life America and the National Right to Life Committee.

The argument in favor of PEPFAR

Supporters of PEPFAR argue that it's still the same program that has enjoyed broad support for 20 years.

"There's no evidence that PEPFAR is funding abortion or providing any support that is going to those prohibited activities," says Jen Kates, director of global health and HIV policy at Kaiser Family Foundation. "So this is really just a political debate, an ideological debate about abortion."

Health workers on the ground say that debate could have real effects on millions of vulnerable people.

"For us in Africa it has always been strictly about finding people who need life-saving medication, seeing that they get on it, seeing that they stay on that treatment," says Dave Clark, group chief operating officer at the Aurum Institute, which promotes public health in South Africa through research and direct care. "It's always been about preventing new infections, especially in babies and children, and it's about ensuring that those children grow up to live a full and productive life free from HIV and TB [PEPFAR targets tuberculosis and various sexually transmitted infections, in addition to HIV and AIDS]. I know from our experience that this is a profoundly pro-life approach."

What might change without reauthorization

If PEPFAR is not reauthorized for its five-year term, some conservatives say a yearly review of the program would give them more oversight over PEPFAR and the ability to nudge policy away from what they see as supporting abortion access.

Even if funding to PEPFAR partners is not in jeopardy in the short term, the bigger danger could be the long-term erosion of a global consensus around fighting HIV, says Jen Kates.

"It would just change the game around what has been one of the few government programs that has been incredibly successful," she says. "The symbolic effect of it not being able to withstand that pressure could have repercussions down the road."

Partner organizations in Africa and elsewhere have warned that such a move would weaken the united front against HIV/AIDS that PEPFAR has helped shore up. And given the volatility of U.S. politics, yearly appropriations fights could put the program's broad mandate at risk.

"HIV doesn't respect one-year funding cycles with their inherent uncertainty," says Clark. "I think HIV will exploit any lapse in our vigilance, as we've seen when COVID occupied the center stage for two years and HIV and TB and programs fell back. Moving from a five-year [funding] approach to an annual stopgap approach will bring about a rekindling of uncertainty, when certainty was actually the watchword of what PEPFAR achieved."

Besides the uncertainty, failure to fully reauthorize PEPFAR risks allowing a handful of specific provisions to lapse. One is the requirement that half of the program's funding be spent on direct care and another mandating that 10% of PEPFAR funding go directly to orphans and other children affected by HIV. Congress could bring back these provisions, but it would require an additional vote.

Some advocates of PEPFAR say discarding those requirements would actually give the program a freer hand to spend its money as it sees fit.

Partner organizations such as TB HIV Care say they could likely still manage if PEPFAR becomes an annual political football, but they worry that it would be the beginning of an erosion in America's commitment to take on the HIV/AIDS pandemic.

"Life expectancy in South Africa has increased from 54 years in 2004 to 60 years in 2022 as a result of all of the HIV services and the other kinds of support provided in partnership with the government. The HIV incidence has decreased in children by 59%," says Harry Hausler. "I think it's important for the American people to think about what a great impact they've already had and how grateful developing countries are for this support and how crucial it is for it to be sustained."

This week, Rep. Chris Smith introduced an amendment to the appropriations bill that would restore the Mexico City Policy to PEPFAR, saying from the House floor: "We ask that PEPFAR remain true to its original mission and respect our norms, traditions and values. We ask that those partner organizations with whom the U.S. government partners to implement PEPFAR programs in ways that are cognizant and respectful of our beliefs and not cross over into promoting divisive ideas and practices that are not consistent with those of Africa."

The bill is not expected to pass in its current form. In the meantime, Aurum's Dave Clark says organizations like his will continue doing the work, while keeping a vigilant eye on the U.S. Congress.

"My view is that the American people have always known how to begin a good work, and they've always summoned the stamina to see a good work through to the end," Clark says. "PEPFAR is about saving lives, and to that end, it is for me undoubtedly one of the most profound gifts to global health the world has ever seen. It would be a great pity if that gift was somehow undone."

NPR global health correspondent Nurith Aizenman contributed reporting to this story.