A deal on 100% debt relief for the world's poorest countries can be secured at July's G8 summit in Scotland, the chancellor has said.
Gordon Brown is confident progress will be made at Gleneagles
Gordon Brown said countries paying more on debt interest than education or health would not have much of a future.
The lead-up to the summit at Gleneagles will see tens of thousands of people take part in a Make Poverty History march in Edinburgh on Saturday.
Protesters wearing white plan to form a white band around the city centre.
The chancellor told BBC Scotland's The Politics Show that 100% debt relief would happen.
He said: "If you're actually spending more in debt interest payments than you can spend on education, then as a country, you're not going to have much of a future.
"And if you've got to spend more on debt interest payments than you spend on health, then there are lots of people going to die unfairly and unnecessarily.
"So I think the rest of the world has come to realise that 100% debt relief is essential, I believe we've got an agreement now that that should happen, I think you'll find it confirmed at the Gleneagles summit."
Mr Brown said it would cover the 38 poorest countries, tied to conditions of transparency and guarantees that the money goes to health and education.
Oxfam in Scotland spokeswoman Judith Robertson called on more ambitious targets to make a real difference to people's suffering.
Billy Bragg will be joining stars at the Edinburgh rally
She said: "The figures he was talking about amount to about £1.4bn cancellation of debt a year.
"We and other organisations who are part of Make Poverty History have estimated that it's going to take more than £10bn a year to support the countries to meet the UN Millennium development goals, which are the targets agreed internationally."
Scottish National Party Westminster leader Alex Salmond welcomed a raised awareness of the problems facing poor nations, but warned against presenting partial steps in tackling the problem as a "total solution".
He said: "The reality about the debt agreement to date from the finance ministers is it covers about one-sixth of African debt and hardly touches the economic power-houses of the continent like Kenya and Nigeria."
Meanwhile, the head of the Catholic Church in Scotland will tell marchers in Edinburgh he is "scandalized by the needless suffering poverty causes".
Cardinal Keith O'Brien is to be one of the platform speakers to address the rally in The Meadows on Saturday.
He will describe poverty as "a crime against humanity, a great injustice," adding, "to be passive or indifferent is to be an accomplice in barbarity".
International Development Secretary Hilary Benn will also join marchers in Edinburgh on Saturday.
Mr Benn said: "We can't claim any more that we don't know what's going on. We see the lives that far too many of our fellow human beings live and we're in an age when we can do something about it.
"I think it is the great moral challenge of our generation."
He said protest organisers were working closely with police in Edinburgh, adding: "I hope lots of people will turn up, the most important thing is that it is a safe demonstration."
Organisers of the Make Poverty History event have announced that celebrities including pop star Daniel Bedingfield and actors Billy Boyd and Pete Postlethwaite will be showing their support.
Broadcaster Jonathan Dimbleby and singer-songwriter Billy Bragg are to host stages at the event, which is expected to attract thousands to the city.
A range of Make Poverty History underwear has been launched
Protesters who take part will also be able to see highlights of the London Live 8 concert on big screens.
Richard Bennett, chairman of the Make Poverty History Campaign, said it was time for people to make their voices heard.
"The 2nd of July...will be the day when the people of Scotland and the UK add their voices to those from Africa, Asia and Latin America to send a loud and clear message to the G8 that now is the time to end the tragedy of thousands dying from poverty," he said.
On Sunday, the Make Poverty History campaign unveiled designed boxer shorts and hot pants for supporters not content with sporting the organisation's white band on their wrists.
More than 100 enthusiastic supporters gathered on Edinburgh's Calton Hill to show off the fair trade underwear, which features a white waistband with the words Make Poverty History.