U2 frontman Bono has had a "good old row" with President George Bush about Aids funding during a White House meeting.
Bono said he was "disappointed" with the talks
The rock star urged the US president to allocate $3bn (£1.9bn) to fight the current Aids crisis in Africa.
But the Bush administration would not increase its previous $2bn (£1.26bn) pledge, citing concerns the money would not be used effectively.
Bono described Bush as "sincere" but added: "What I just can't agree with him on is the numbers."
In January, the US pledged to increase the country's Emergency Plan for Aids Relief budget by $10 billion (£6.28bn) to $15 billion (£9.43bn) over the next five years.
At the time, the US agreed it would spend $2bn out of this year's budget, but Bono has now called for this to be increased to $3bn.
But Mr Bush has held back on pledging the full amount because of concerns about how the money will be allocated.
"You need to make sure the infrastructure is in place for those resources to be spent," White House spokesman Scott McClellan said.
He added that spending would increase over the coming years to meet the $15bn commitment.
Bono and Mr Bush first discussed Aids funding in January
Following Bono and Mr Bush's meeting in Washington, the U2 frontman said he was "depressed" at not influencing the president's stance.
The Aids initiative will provide anti-viral treatment for HIV sufferers in Africa and the Caribbean.
It would also go towards education and prevention as well as helping children affected by the disease.
"The Aids emergency is just that. It's not a cause. We're
not here peddling a cause. We're not looking to get into
America's wallet for another cause," Bono said after the meeting.
"Several thousand people dying a day is not a cause, it's an emergency."