The Global Fund, a multi-lateral body which channels funding for projects to combat the diseases, opens a three-day conference to boost its coffers in Berlin on Wednesday.

The diseases kill 6 million people a year, say campaigners.

Rock star Bono, long involved in the campaign to fight poverty, urged countries to pay up.

Britain said on Tuesday it would contribute US$2.0 billion up to 2015, including 360 million pounds for 2008-2010. Campaigners denounced the commitment as being only half the amount Britain had previously pledged.

In June, Britain and other Group of Eight industrialised nations committed to US$6-US$8 billion per year replenishment of the Global Fund by 2010 at a summit hosted by Germany.

The Fund claims to have saved 2 million lives since it was created in 2002 through partnerships with governments, the private sector and local communities.

Overall, the Fund needs US$12-18 billion for the next three years but some major contributors, including Japan and the United States, will not make pledges in Berlin as the timing does not fit their budgetary cycle, said the Fund's Jon Liden.

France, Germany and Scandinavian nations are among those set to make the biggest commitments.

Since 2001 the Fund has signed agreements worth US$7.6 billion for 450 grants in 136 countries.