EDINBURGH, Scotland —  Britain's Treasury chief on Tuesday warned that anti-poverty campaigners may be disappointed when G-8 (search) leaders announce their package of aid to Africa.

Gordon Brown's effort to dampen expectations came as Live 8 (search) organizer Bob Geldof (search) traveled to the Scottish capital, Edinburgh, to step up pressure ahead of the G-8 summit, which begins in Gleneagles on Wednesday. Geldof insisted the British government should not be "lowering the bar" of what the G-8 should achieve.

Brown is a driving force behind British Prime Minister Tony Blair's efforts to make aid to Africa a G-8 priority. The Chancellor of the Exchequer says helping the continent is the "greatest moral crusade of our time" and is pushing for debt relief, free trade and a doubling of international aid.

But he told the British Broadcasting Corp. Tuesday that he'd warned campaigners the G-8 was unlikely to meet their expectations.

"I know that ... you will tell us we've got to do more. I know that what you will say is that what we can achieve is perhaps not good enough," Brown said he'd told campaigners. "But we have got to bring the whole of the world together. What Britain says is one thing, what we can persuade the rest of the world to do together is what we will get as the outcome of Gleneagles."

Leaving London by train for Edinburgh, Geldof said he was "not prepared to be disappointed."

"I don't think that is an option," he said. "I don't think the Chancellor should try lowering the bar at this stage. We have come for victory. It has to happen now. Not to do it now would be grotesquely irresponsible. It is unacceptable for politicians to say 'prepare to be disappointed.'"

Geldof, who masterminded the Live Aid concerts 20 years ago, has called for a million people to take a "Long Walk to Justice" and converge on Edinburgh, where rock acts including Texas and Annie Lennox will take part in a concert on Wednesday titled: "Edinburgh 50,000: The Final Push." Organizers say the figure refers to the number of people who will die that day from extreme poverty.

He was traveling with representatives from anti-poverty campaigns in France, Georgia, Ghana, Mali, Sierra Leone and Britain.

Blair's Africa Commission report calls for debt relief, fair trade and an extra $25 billion a year in international aid for the continent by 2010, and then a further $25 billion annually up to 2015.

Oxfam's head of advocacy Jo Leadbeater warned that 2010 would be "five years too late for the 55 million children who will die waiting for the world's richest leaders to deliver on their promises."