WASHINGTON (AP) — Science now has the tools to slash the spread of HIV even without a vaccine — and the U.S. is donating an extra $150 million to help poor countries put them in place, the Obama administration told the world’s largest AIDS conference Monday.

“We want to get to the end of AIDS,” declared the top U.S. HIV researcher, Dr. Anthony Fauci of the National Institutes of Health.

How long it takes depends on how quickly the world can adopt those tools, he said — including getting more of the millions of untreated people onto life-saving drugs that come with the bonus of keeping them from infecting others.

“No promises, no dates, but we know it can happen,” Fauci told the International AIDS Conference.

Some 34.2 million people worldwide are living with HIV, and 2.5 million were infected last year.

Secretary of State Hillary Rodham Clinton said the goal is an AIDS-free generation. That would mean no babies would be born infected, young people would have a much lower risk than today of becoming infected and people who already have HIV would receive life-saving drugs so they wouldn’t develop AIDS or spread the virus.

“I am here today to make it absolutely clear the U.S. is committed and will remain committed to achieving an AIDS-free generation,” Clinton told the more than 20,000 scientists, people living with HIV and policymakers assembled for the conference.

But it will require smart targeting of prevention tools where they can have the greatest effect — including to high-risk populations that are particularly hard to reach because of stigma.

“If we want to save more lives, we need to go where the virus is,” she said.

First, Clinton said it’s possible to virtually eliminate the transmission of HIV from infected pregnant women to their babies by 2015, by getting the mothers onto anti-AIDS drugs. HIV-infected births are rare in the United States and are dropping steadily worldwide, although some 330,000 children became infected last year. Clinton said the U.S. has invested more than $1 billion toward that goal in recent years and is providing an extra $80 million to help poor countries finish the job.

Much of the AIDS conference is focused on how to get treatment to all people with HIV, because good treatment can cut by 96 percent their chances of spreading the virus to sexual partners. Fauci pointed to South Africa, where healthy people who live in a region that has increased medication now have a 38 percent lower risk of infection compared with neighbors in an area where HIV treatment is less common.

Drugs aren’t the only effective protection. Fauci said male circumcision is “stunningly successful,” too, at protecting men from becoming infected by a heterosexual partner. Clinton said the U.S. will provide $40 million to help South Africa reach its goal of providing voluntary circumcision to half a million boys and men this year.

A tougher issue is how best to reach particularly high-risk populations: gay and bisexual men, sex workers and injecting drug users. In many countries, stigma and laws that make their activities illegal drive those populations away from AIDS programs that could teach them how to reduce their risk of infection, Clinton said.

“If we’re going to beat AIDS, we can’t afford to avoid sensitive conversations, and we can’t afford not to reach the people who are at the highest risk,” she said.

So the U.S. will spend an additional $15 million on research to identify the best HIV prevention tools to reach those key populations in different countries, and then launch a $20 million challenge fund to support country-led efforts to implement that science.

The world spent $16.8 billion fighting AIDS in poor countries, the hardest-hit, last year, and the United States is the leading donor.

But Bill Gates, the Microsoft founder and philanthropist, said the world is facing incredible uncertainty about whether wealthy nations will continue funding AIDS programs with the same vigor as in the past.

“As these budget tradeoffs are made, the voices of the AIDS community and the global health community are going to have to be louder than ever,” said Gates, whose Bill & Melinda Gates Foundation has pledged more than $1 billion to global AIDS efforts.

Another $7 billion a year is needed to get to 15 million people in low- and middle-income countries by 2015, a United Nations goal. A record 8 million received potentially life-saving drugs last year.

“This gap is killing people,” UNAIDS chief Michel Sidibe told the conference. “My friends, the end of AIDS is not free. It is not too expensive. It is priceless.”

The prices of generic AIDS drugs in developing countries are dropping every year. One philanthropy, the Clinton Health Access Initiative, said 70 countries in Africa, Asia, Eastern Europe, Latin America and the Caribbean that participate in its drug-procurement program now can purchase the main combination for less than $200 a year.

“We have to be innovative,” said Sheila Tlou, the former health minister of Botswana, now with UNAIDS. “We have to look at new ways of funding.”

Speaking to the conference via video, French President Francois Hollande said his country was doing that by beginning what’s called a financial transaction tax next month. The tax idea has received a lukewarm reception in other parts of Europe and the U.S.

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Associated Press Writer Joshua Lederman contributed to this report.