LONDON (Reuters) - International aid financing and innovation has helped to save nearly 700 million lives in the past 25 years, but those gains could be lost if momentum and political will wane, global health experts said on Monday.

A report by international aid advocacy group the ONE Campaign said the progress against preventable deaths and diseases since 1990 could stall, and even go into reverse, unless donor governments make new commitments to innovation and action.

The good news is that the world knows what it takes to succeed, said the report, released to coincide with a conference on global health in Berlin this week.

“The lives saved amount to twice the population of the United States,” said Gayle Smith, the ONE Campaign’s chief executive. “We’ve shown that we can do this, and to slow down – or step back – at this critical juncture would be to leave progress on the table.”

The report said international development assistance for health rose to a peak of $56 billion in 2013 from $20.4 billion in 2000. By 2015, it had fallen back a little to $51.8 billion.

During the five years from 2010 to 2015, maternal mortality in sub-Saharan Africa fell by 15 percent, under-five deaths dropped by nearly a third, and AIDS-related deaths fell by nearly 40 percent.

But the report said donor assistance for global health has flat-lined since 2014, even though about 7,000 people still die each day of the preventable diseases AIDS, tuberculosis or malaria - most of them in the poorest countries in Africa.

The international community is “severely off track” to reach United Nations global health targets – agreed by 193 countries and known as the Sustainable Development Goals – by 2030, the report said.

It called on donors, governments and philanthropic organizations to “mobilize more money for health and deliver more health for the money”, arguing that such investments would pay off by boosting Africa’s economic output and stability.

In fewer than 50 years, it said, there will be more young people in Africa than in all G20 countries combined. “Ensuring that this population is healthy, educated and empowered will yield a demographic dividend that could fuel the future of a continent and enable Africa to propel the global economy.”

(The story is refiled to add dropped word “will” in first paragraph.)