One in five United Nations Global Fund projects designed to fight the world's deadliest diseases have not met their targets, according to a report.
Aids projects have proved the most successful, the report says
The results are revealed in the fund's own analysis of an initial 25 Aids, TB and malaria projects in 15 countries costing $158m.
It blames political problems in the countries where they are based.
The Global Fund was conceived by UN Secretary General Kofi Annan as a means of fighting the main killer diseases.
It is backed by private donors and Western governments.
The first round of grants was agreed two years ago and the programmes have been up and running for a year.
The Global Fund is now in a position to judge whether or not they are providing value for money.
Those projects failing to meet targets are unlikely to receive further funding.
The report says the programmes operated by non-governmental organisations (NGOs) tend to be more successful than those run by governments.
And it concludes that expanding existing health programmes works better than starting up new projects.
The programmes varied greatly in size from a $220,000 grant to the Kenya Network of Women with Aids to a $25m programme run by the Chinese government to increase the nationwide coverage of TB treatment and control.
Twelve of the 25 programmes were on track or substantially achieved their targets, the fund says.
Among the success stories was a programme to provide anti-retroviral drugs to people with Aids in Honduras, which treated nearly twice as many people as it expected to.
Eight programmes were judged to have made substantial progress but had fallen short of their targets. Delays in the procurement of drugs and other commodities were often to blame, the report says.
Five grants in three countries were subject to substantial delays. The report blames bureaucratic hold-ups or problems within health ministries.
HIV/Aids grants are reported to have the best results compared to targets. This is to a large extent the result of the particular drive and commitment of key health personnel or senior politicians.
Nearly 2.3 million people have benefited from the programmes.
There is still a funding gap, however.
Current pledges to the fund are expected to peak at $3bn a year by 2008, of which just over half will be spent on Aids. The fund says it needs twice that amount.
The report was launched in the Thai capital Bangkok, where the world's largest gathering of Aids experts and campaigners gets under way on Sunday.
The 15th International Aids conference will be opened by Mr Annan.
A protest march demanding a better deal for poorer countries is due to take place before the official opening ceremony.
Demonstrators plan to highlight the inequalities of Aids treatment across the globe.