Efforts to tackle diseases which kill millions each year could be badly affected by a severe shortfall in donations to a worldwide funding body.
The Global Fund to Fight Aids, TB and Malaria will make no new grants until 2014, and there is a threat to some existing projects.
It asked international donors for $20bn, but received just $11.5bn.
This misses even the fund's "minimum" $13bn target, which it says is needed to maintain programmes until 2014.
HIV charities said they were "extremely alarmed" by the decision.
This is the first time in its 10 year history that the fund has been forced to cancel its three-yearly funding round.
It blames the problem on a combination of "substantial budget challenges" in some of the countries who would normally contribute, and low interest rates cutting returns on its investments.