Tue 04 Apr 2003US forces outgun Iraqis as Baghdad grip tightensUS forces are tightening their grip on central Baghdad, advancing street by street and blitzing targets with planes and tanks as Iraqi defenders fight an apparently hopeless battle with anti-tank weapons and rifles.Consolidating the stranglehold on the city of 5 million people, US Marines captured the Rashid air base in the southeast, three miles from the centre.