By Matt Spetalnick

WASHINGTON, June 10 (Reuters) US-led troops and Iraqi forces will capitalize on Abu Musab al-Zarqawi's death by cracking down on insurgents trying to regroup after losing their leader, President George W Bush said today.

Bush's vow was another signal that the United States was not ready to start scaling back its military presence despite the killing of al Qaeda's chief in Iraq, mastermind of the bloodiest bombings since the American-led invasion in 2003.

''Coalition and Iraqi forces are seizing this moment to strike the enemies of freedom in Iraq at this time of uncertainty for their cause,'' Bush said in his weekly radio address.

Bush hailed Zarqawi's killing in a US air strike on Wednesday as ''an important victory in the global war on terror,'' but he maintained the sober tone that has marked the administration's reaction.

Despite pressure from some Democrats to start bringing troops home, Bush -- struggling with growing anti-war sentiment and low approval ratings -- set no timetable for withdrawal and repeated his warning to Americans to expect further sacrifice.

He yesterday said that the death of Zarqawi, a Jordanian militant leader, would not end the war but would ''help a lot.'' More Reuters SI RS2027