US President George W. Bush on Thursday hailed the "durability" of advances in Iraq and announced shorter tours of duty for US soldiers as he hinted more troop reductions could come later this year. Speaking outside the White House, Bush said the US troop surge had helped reduce violence while Iraqi forces built up strength, and pointed to progress in negotiations toward a deal on the continued presence of US troops there. Still, Bush cautioned that the gains could be "reversible," even as Pentagon figures showed that 11 US soldiers were killed in Iraq in July, the fewest to die in a single month since the invasion five years ago.