A coalition of campaigners, including the rock star Bono, is increasing pressure on the Bush administration to increase funding to combat the Aids pandemic in Africa, amid signs that momentum on the issue in the US has flagged.

Next week, Bono and other campaigners, including African activists and the film star Ashley Judd, will take a "heartland tour" across seven Midwestern and southern states in an attempt to raise awareness about the spread of HIV-Aids. Tomorrow, a demonstration in Washington will draw attention to the modesty of US donations to the Global Health Fund set up to combat HIV, tuberculosis and malaria since Bono's high-profile trip to Africa with Paul O'Neill, the Treasury secretary, in May.

The US is the largest single donor to the fund, but its contribution has fallen well short of the $2.5-$3bn called for next year by the fund's leaders.

Jim Kolbe, chairman of the influential House foreign operations appropriations sub-committee, recently called for a one-year freeze on overseas Aids funding. A bill sponsored by Bill Frist, Republican senator from Tennessee, and John Kerry, Democrat from Massachusetts, which would have provided more than $4bn over the next two years for overseas Aids funding, was blocked in the Senate last week.

The campaigns come ahead of a planned trip to Africa by President George W. Bush early next year.

Paul Davis of Health Gap coalition, a campaign network, said that the presidential initiative on HIV-Aids announced earlier this year was inadequate. "President Bush is a man with no plan," he said. "A true leader of the world would not simply repackage existing moderate programmes."