The world's superpower is throwing its weight around for the benefit of Africa

The unexpected emergence of an African concert party to put pressure on Robert Mugabe to stand down as ruler of Zimbabwe owes much, as we report today, to American diplomacy.

However much we disliked Tony Blair's strategy of trying to influence the American hyperpower from as close to within as possible over Iraq, this suggests it need not always be wrong.

Indeed, in adding urgency to the US push for peace between Israelis and Palestinians, Mr Blair has already received some return on the blood price that Britain paid in Iraq. President George Bush's attention to Northern Ireland may have been to no immediate avail, but it was welcome nonetheless. Now it seems that the US is using its power in another benign cause.

For all that American diplomacy can be derided as a contradiction in terms, for all that it is easy to mock the blunderings that managed to turn a world united in solidarity with the US after 11 September 2001 to one mostly opposed to it over Iraq, it can still be a power for good.

Of the many paradoxes of this hopeful turn of events, another is that the Blair government's policy towards Mr Mugabe has often been uncertain. Part of that is understandable. As the former colonial power, Britain has to be careful not to strengthen Mr Mugabe by playing the role assigned to it in his racist propaganda, of the white oppressor. Far better that the pressure on the dictator come from wider world opinion, and from the leaders of black Africa in particular.

Equally, though, there was more the British government could have done to isolate and demoralise the Mugabe regime, especially after the blatantly undemocratic elections last year. There were sound arguments against economic sanctions, as the plight of the Zimbabwean people is desperate enough as it is – and has become so much worse in recent months. But a sporting boycott would have underscored the extent to which Mr Mugabe is regarded as an international pariah, if only the Government could have given a clear and early lead. It is still not too late for Mr Blair to stop a return tour by the England Test team in Zimbabwe.

This argument is, however, a sideshow to the real drama, which will be played out when Thabo Mbeki, the South African President, visits Mr Mugabe on Monday with Olesegun Obasanjo of Nigeria. The deal seems to be that Mr Mugabe will be praised to the skies in public while privately being encouraged to retire, with immunity from prosecution for human rights abuses. He could be replaced by Simba Makoni, his former finance minister, who would then share power with the opposition Movement for Democratic Change until new elections.

This represents a welcome change in policy on the part of South Africa, the only regional power that is capable of forcing regime change in Zimbabwe from the outside. And there is no doubt that economic pressure from the US has helped bring it about.

For all Jacques Chirac's principled resistance to American adventurism in Iraq, the French President has behaved disgracefully in seeking to undermine European Union travel restrictions on Mr Mugabe and his cronies.

In this case, America is stepping up to its responsibilities as the sole superpower. It is using its wealth and power to help improve the condition of Africa. For all his mistakes over Iraq, Mr Blair deserves unstinting praise for his role in working to heal what he has described as the scar on the conscience of the world.