First New York and Madrid, now London. Americans woke on Thursday to an eerily familiar newsflash: a synchronised terrorist attack on a western capital.

The blasts in London were not on the scale of the grisly spectacle of September 11, but their murderous intent was the same. So was the political import of the attacks. The target was Britain, America's most steadfast ally in President George W. Bush's declared war on terror.

In the past six months, it has become fashionable to underplay the war on terror. Mr Bush uses the slogan less regularly. Even as billions continue to be poured into homeland security, the president's domestic priorities have shifted to pension, tax reform and filling the new vacancy on the Supreme Court.

Abroad, the Iraqi insurgency aside, he has been coaxed into joining the discussion on global warming and debt relief for Africa, both of which head the agenda at this week's G8 summit in Gleneagles, Scotland.

Much of the pressure on Mr Bush to focus on these “soft security” issues has come from Tony Blair, the British prime minster chairing the Gleneagles meeting. Mr Blair believes that Africa, the environment and ending poverty demand attention in their own right; but there is a sense, too, that the British government thinks the Gleneagles agenda is much more appealing than the hard-edged war on terror.

Mr Bush on Thursday highlighted the contrast between the work of the G8 summit and the terrorists as “incredibly vivid”. He added: “On the one hand, you have people working to alleviate poverty and rid the world of the pandemic of AIDS and ways to have a clean a environment, and on the other hand, you have people working to kill other people.”

After 9/11, Alan Greenspan, chairman of the Federal Reserve, was among those who similarly drew a contrast between the crushing negativism of the September 11 suicide bombers and the creative impulses of Americans and others who build companies, open markets and keep the world economy going.

Yet in the run-up to the G8, a number of talking heads on US television wondered aloud whether world leaders were allowing themselves to become distracted by the well-meaning but vague campaign to “make poverty history”, rather than dealing with the pressing but daunting national security threats of nuclear proliferation and the insurgency in Iraq. Now the conversation will inevitably switch back to Mr Bush's agenda.

The airport security checks will become even more rigorous, the police presence on the streets more intrusive. Washington will look even more like a capital under siege. The pressure on civil liberties will increase all in the name of national security.

Republicans are bound to draw contrasts between woolly-minded Democrats who focus on the causes of terrorism and the self-styled realists determined to triumph in a war without mercy against radical Islamic fundamentalism. Democrats will respond that Mr Bush's war has made the world no safer.

As Britons rally in the face of adversity, and Tony Blair again demonstrates the quality of leadership, Mr Bush will feel vindicated. In continental Europe, they will be asking: who is next?