Writing in Britain's Financial Times newspaper, Rumsfeld said "extremists" had been killing people in attacks around the world for at least 20 years before the arrival of US troops in Afghanistan and Iraq.

"The extremists do not seek a negotiated settlement with the west," he wrote. "They want America and Britain and other coalition allies to surrender our principles.

"Some seem to believe that accommodating extremist deman-ds, including retreating from Afghanistan and Iraq, might put an end to their grievances, and, with them, future attacks," he added.

"But consider that when terrorists struck America on September 11 2001, a radical Islamist government ruled Afghanistan ... and Saddam Hussein tightly clung to power in Iraq."

Rumsfeld said those behind such attacks would always offer "empty justifications" to try to explain their actions.

"They seek to destroy things they could never build in 1,000 years and kill people they could never persuade," he wrote.

His comments echo those of British Prime Minister Tony Blair, who said last week there was no justification for attacks which killed 52 people along with the four bombers in London on July 7 and second wave of bombs two weeks later which failed to explode.