PORT-AU-PRINCE - US Black Hawk helicopters swooped down on Haiti's wrecked presidential palace to deploy troops and supplies on Tuesday as a huge relief operation to help earthquake survivors gained momentum. The airborne troops in combat gear moved to secure Port-au-Prince's nearby General Hospital, where staff have been overwhelmed by huge numbers of seriously injured patients. Their dramatic deployment to help speed up logjammed aid efforts brought crowds of quake survivors camped out in the park opposite the palace rushing to its iron railings to gawk and beg for handouts of food. It was the most visible and potentially sensitive deployment so far by the US military, which is spearheading international efforts to assist millions of Haitians left injured or homeless by the devastating earthquake a week ago. Venezuela's socialist President Hugo Chavez, a fiery critic of what he calls US "imperialism", has accused Washington of "occupying" Haiti under the pretext of an aid operation. The commander of the U.S. troops in Haiti, Lieutenant General Ken Keen, said their primary purpose was humanitarian assistance and providing food and water to Haitians, but that there was also a security element to the operation. "Security goes hand-in-hand with our mission," he told CNN at the hospital protected by his men.