Edinburgh, Scotland ? Activists kept up pressure on leaders of the world’s richest nations Tuesday to lift Africa out of poverty, but Britain’s Treasury chief said those who believe human misery can be eliminated “with the stroke of a pen” may be disappointed by the results of this week’s G-8 summit.

As Irish singer Bob Geldof – energized by his Live 8 concerts’ success – joined the demonstrators in Scotland, police warned they will crack down on any further violence by anarchists and others bent on spoiling the summit. About 100 arrested during clashes a day earlier appeared in court Tuesday.

The Make Poverty History campaign launched around the summit has been endorsed by the Dalai Lama, Pope Benedict XVI and Nelson Mandela, along with scores of others around the world.

They have something of an ally in British Prime Minister Tony Blair, who holds the G-8 presidency and hosts the three-day summit opening today at nearby Gleneagles. He has made Africa and climate change the central themes of Britain’s G8 presidency, and he describes global warming as “probably the most serious threat we face.”

The protesters find themselves in the unusual situation of being at least theoretically in agreement with the host government, and their protests to date have not been very violent.

But some of the protesters are anarchists opposed to the G-8 in principle, and they could yet explode in anger. There are fears they may try to stop leaders from getting to the elegant Gleneagles golf resort where the summit is being held, or even try to breach the tightly protected five-mile security perimeter.

Geldof said Britain was pushing hard for a deal to help Africa, but sounded pessimistic. “I am not sure the others want to do it, which will be a grotesque failure,” Geldof said.