Thousands of experts and activists descend on Amsterdam Monday to bolster the battle against AIDS amid warnings that "dangerous complacency" may cause a resurgence of the epidemic that has already killed 35 million people.

Rather than closing in on the goal of "ending" AIDS, new HIV infections have surged in parts of the world as global attention has dwindled and funding levelled off, say leaders of the anti-AIDS movement.

And they lament that too fine a focus on virus-suppressing treatment has overshadowed basic prevention with the result that HIV is still spreading with ease among the most vulnerable people.

"The encouraging reductions in new HIV infections that occurred for about a decade has emboldened some to declare that we are within reach of ending AIDS," said Peter Piot, a veteran virus researcher and founder of the UNAIDS agency.

However, "there is absolutely no evidence to support this conclusion," he insisted, and warned: "the language on ending AIDS has bred a dangerous complacency."

This was evident from declining global and domestic funding for HIV eradication and treatment programmes, Piot said at the launch this week of a report by the International AIDS Society (IAS) and The Lancet medical journal.

The authors of that report, he said, "are extremely concerned that there is a real risk that the world will declare victory long before our fight against AIDS is over."

Rubbing shoulders with celebrity activists such as actress Charlize Theron, Britain's Prince Harry, and singers Elton John and Conchita, more than 15,000 delegates are expected in the Dutch capital for the conference, opening Monday.

- Charlize and Conchita -

While high-profile speeches will seek to revive the flagging fight, the five-day event will also present an opportunity for scientists to mull over recent advances and setbacks in the quest for simpler, better anti-HIV drugs.

More than three decades of research have yet to yield a cure or vaccine for the AIDS-causing virus that has infected nearly 80 million people since the epidemic burst onto the world scene in the early 1980s.

UNAIDS founder Peter Piot warned against growing complacency that an end to AIDS was within reach DON EMMERT, AFP/File

A UNAIDS report Wednesday said about 36.9 million people last year were living with the virus which, thanks to antiretroviral therapy (ART), is no longer a death sentence.

It reported the lowest annual death toll in two decades, and a record number of people on life-saving treatment.

But the report also alerted that new HIV infections are rising in about 50 countries, and have more than doubled in eastern Europe and central Asia.

IAS president Linda-Gail Bekker told AFP that there may have been "a strategic mistake on the part of the AIDS gurus" to prioritise treatment at the expense of preventing HIV infection -- the only real way to stop the epidemic.

AIDS: unequal access to treatment Cecilia SANCHEZ, AFP

"There is no epidemic that we have treated our way out of," she said, citing Ebola and tuberculosis.

"Clearly, a vaccine is the holy grail, but we are not there yet."

In the meantime, the world needs a renewed focus on prevention, said Bekker -- stressing condom use, expanding the use of virus-suppressing ART as an infection shield, and providing safe, infection-free needles to drug users.

But to do this while also getting treatment to the 15.2 million infected people who do not yet have access, the world needs cash.

And this at a time that the US administration under Donald Trump has vowed to cut AIDS spending.

A report this week by UNAIDS and the Kaiser Family Foundation, a health policy NGO, found that after two years of declining global funding, donor payments to low- and middle-income countries rose 16 percent to $8.1 billion (seven billion euros) last year.

- Don't walk away -

But it cautioned this was no cause for celebration, as the trend was "not expected to last".

The extra money came mainly from a rollover to 2017 of funds the US government -- by far the largest funder of AIDS programmes -- had appropriated but not spent in previous years.

Funding from donor governments "is likely to fall again", said the report.

According to UNAIDS, the global effort is short about $7 billion per year to achieve the goal of ending AIDS as a public health threat by 2030, by reducing new infections and deaths by 90 percent from 2010.

New HIV infections are rising in about 50 countries MARCO LONGARI, AFP/File

"The job is not done," stressed Robert Matiru, director of operations at Unitaid, a non-profit body that channels financing for HIV research and development.

"We need people to not only continue to fund... but even increase it."

Bekker fears that "people have walked away to soon" from the fight.

"We're either moving forward in this epidemic, or we're sliding back," she warned.

"The minute you take your eye off the ball, infections will resurge and we will see this thing take off again."