Heads of state, chief executives and global health leaders have gathered in France to try to raise at least 14 billion dollars (£11.4 billion) to finance the fight against Aids, tuberculosis and malaria over the next three years.
French President Emmanuel Macron, who is hosting the conference in the city of Lyon, wants the event to raise a larger amount than the 12.2 billion dollars (£9.9 billion) brought in at the last conference in 2016.
A dozen heads of state and government, mostly from African countries, are attending the two-day conference of the Global Fund.
In his opening speech, Mr Macron urged leaders to accelerate their donations.
“If we meet our commitments in the next three years, 16 million lives can be saved,” he said.
“We must reach 14 million dollars in the next three hours.”
He said France has raised its pledge by 15% to 1.24 billion euro (£1.1 billion).
The US Congress has approved a commitment to give a total of 4.7 billion dollars (£3.8 billion) over three years, while Britain has pledged £1.4 billion.
The donations from governments, philanthropic donors and the private sector will be used to finance health programmes in more than 100 countries.
Major recipients of the fund will be Nigeria, Tanzania, the Democratic Republic of the Congo, Mozambique and Zimbabwe.
The Global Fund said the money would help avert 234 million infections and try to get back on track to end HIV, tuberculosis and malaria as epidemics by 2030.
The organisation said the programmes it has supported since its creation in 2002 have saved 32 million lives.