Bono- friend of Warren Buffett, Rupert Murdoch, Billy Graham, Pat Robertson

There have been dinners with Brad and Jennifer and drinks with Tom Hanks and Cameron Diaz. So far, so routine for a rock star on a mission. But the sharpest advice Bono received on how to win American hearts and minds around to his crusade on Africa came from an altogether less expected source: the legendary stock market investor Warren Buffett.

The Irish rock star, who has arguably done more than any other to ensure that the cause of Africa gets on to the agenda of the US administration, has stepped up his lobbying while on U2's Vertigo tour in the US over the last two months to increase the pressure in the run-up to the G8 summit next month in Gleneagles.

Earlier this week he told the Guardian in Cologne how advice from Buffett, reportedly the second richest man in America, had shaped his strategy: "Warren Buffett told me, 'Don't appeal to the conscience of America, appeal to its greatness, and I think you'll get the job done'."

Others enlisted in Bono's crusade have included the media mogul Rupert Murdoch, the former Republican senator Jesse Helms, and figures on the religious right such as Pat Robertson and Billy Graham. The rock star described in his only newspaper interview before next month's G8 summit how he has shared a laugh with President Bush, whom he describes as "very funny".

He has not been afraid to use his Christian faith to appeal to the American religious right, dining with Billy Graham and his son Franklin, and quoting Gospel verses to Jesse Helms, which reduced the 83-year-old Republican to tears.

Bono has spent six years trying to change the mindset of the world's most powerful country in relation to its poorest continent, risking his own reputation and that of his band by associating with some of the most controversial figures in American public life.

At each of the 27 concert dates in the US over the last two months, he has made a direct pitch to audiences of more than 50,000 fans to sign up to the US One campaign, telling them: "My first experience of America was watching Neil Armstrong on the moon. America looked like a place where anything could happen. That's what we're asking Bush - to bring mankind back to earth. We have the technology, we have the resources and the knowhow, but do we have the will?"

Every night, the crowds shout back, 'yes'. "Even in Arizona where the word 'poverty' isn't in the lexicon and where people tell me there are a lot of Republican whites, they were shouting yes," Bono said.

During U2's tour, the One campaign has gone from 50,000 registrations to a million. In the last 10 days, the campaign was boosted further from the airing of a documentary of Brad Pitt on a trip to Africa with Data, the organisation Bono has co-founded (Debt, Aids, Trade, Africa).

"Brad and Jennifer [Aniston] a year ago put together a dinner for 20 great actors and asked me to speak. Tom Hanks, Julia Roberts and Cameron Diaz were all there, and they have all followed through. Sean Penn, George Clooney and P Diddy have all come to me, saying, 'We see you're there, we want to help. What can we do?'"

What has made the One campaign work, in Bono's view, is the combination of Hollywood and what he calls "heartland". That includes the Christian music industry, which has promoted a letter-writing campaign to President Bush on Africa, urging "Christians of conscience" to get involved.

Bono has also been able to draw in help from new technology corporations such as AOL, and has described Murdoch as "very helpful".

Murdoch lobbied Karl Rove, White House chief of staff, and cleared free airtime on his Fox TV network for One campaign adverts in the run-up to the G8. "Rupert said, 'I'm not going to lead the charge but if we make progress, I'll support you,'" Bono said.

The rock star tells his American audience in media appearances from the Oprah Winfrey show to interviews with Bill O'Reilly, the outspoken commentator for Fox News, that the "stupid poverty" in which thousands of Africans die every day from a mosquito bite must be the cause of this generation, just as civil rights was the cause of an earlier generation.

Bono points to a number of breakthroughs in American policy on Africa as signs that his campaigning is paying off. The US signed up to the 100% debt relief package agreed last weekend at the G7 finance ministers' meeting in London. He also cites the fact that aid to Africa has nearly trebled under George Bush and the US in 2003 initiated a $15bn (£8.2bn) five-year programme on Aids.

He was personally credited with the dramatic public U-turn on Aids of Jesse Helms. "Christ only speaks about judgment once and it's not about sex but about how we deal with the poor, and I quoted Matthew, 'I was naked and you clothed me, I was hungry and you fed me.' Jesse got very emotional, and the next day he brought in the reporters and publicly repented about Aids. I explained to him that Aids was like the leprosy of the New Testament."

When Bono was told that there was no support from the grassroots for action on Aids in Africa, he took a choir of Ghanaian children, the US film star Ashley Judd and a Ugandan woman who was HIV positive around the mid-west in 2002, visiting seven states in a week. It was on this same tour that Bono met Warren Buffett.