The killing of militant Abu Musab al-Zarqawi at the same time Iraq finished forming its government was "a stunning shock" to al-Qaeda, US Defence Secretary Donald Rumsfeld said last night.
"A stunning shock to the al-Qaeda system," Mr Rumsfeld said of the death of Zarqawi and five others in a US bombing in Iraq.
"On the very day he gets killed, the government gets formed," he told reporters on his plane home to Washington from Brussels, where news of Zarqawi's death upstaged a Nato ministerial meeting.
Replacing Zarqawi "is not impossible but it takes time, it takes effort," Mr Rumsfeld said. US authorities said Zarqawi directed the killings of thousands of Iraqis and was the pivotal link between al-Qaeda in Iraq and the wider network of Osama bin Laden,
Mr Rumsfeld said it was not immediately clear who might succeed the Jordanian-born Zarqawi.
"I'm sure that the intelligence people could probably tell you two or three people who had various roles and who would be likely prospects," said Mr Rumsfeld. "It could also be somebody outside the Iraqi network."
Asked if he expected a surge of retaliatory violence in Iraq, the Pentagon chief said many attacks were planned in advance, unconnected to daily events.
"You can have an upswing but I think linking it to that would surprise me," he.
Mr Rumsfeld hailed Iraqi Prime Minister Nuri al-Maliki for finally naming interior and defence ministers and averting a crisis in the Shia Islamist's three-week-old unity government.
"He's the kind of person who can make decisions, he can make tough decisions. He's willing to stick to his guns, and I think his early months as a relatively new political leader in Iraq, one has to give him very high marks," he said.