United States Defence Secretary Donald Rumsfeld has warned of a 'long, hard war' and more 'tragic days' in Iraq.

His made the statement while mourning the deaths of 15 soldiers whose helicopter was shot down in Iraq.

"It is clearly a tragic day for America and for these young men and young women. Our prayers have to be with them and with their families," he said on ABC-TV.

Also See: US chopper downed in Iraq; 15 killed

"In a long, hard war, we're going to have tragic days, as this is. But they're necessary. They're part of a war that's difficult and complicated," he said.

The people who are firing surface to air missiles, he said, are the same people who are killing Iraqis and who had tortured people.

He, however, pointed out that the US had no proof that Saddam was masterminding the attacks on the US-led forces.

"We do not have hard evidence that he is coordinating this," he said. The level of unrest, he added, would be 'probably not very difficult' even if Saddam was captured.

On both ABC-TV and on NBC-TV on which he appeared earlier, Rumsfeld stressed that the US will fight on till victory against global terrorism but warned that the war will not be over as long as more terrorists are being turned out in madrassas.

He said the US would continue its efforts to stabilise Iraq despite a deadly attack. "The president has every intention of staying after the terrorists and the countries that harbour terrorists until we have won the war," he said.