At first light Wednesday, a U.S. Coast Guard helicopter evacuated four critically injured U.S. Embassy staff to the hospital on the U.S. Naval base at Guantanamo Bay, Cuba, where the military has been detaining suspected terrorists.
President Barack Obama promised an all-out rescue and humanitarian effort, adding that the U.S. commitment to its hemispheric neighbor will be unwavering.
"We have to be there for them in their hour of need," Obama said.
A small contingent of U.S. ground troops could be on their way soon, although it was unclear whether they would be used for security operations or humanitarian efforts. Gen. Douglas Fraser, commander of the U.S. Southern Command, said roughly 2,000 Marines as part of an expeditionary unit might be deployed aboard a large-deck amphibious ship. Fraser said the ship could provide medical help.
Other nations — from Iceland to Venezuela — said they would start sending in aid workers and rescue teams. Cuba said its existing field hospitals in Haiti had already treated hundreds of victims. The United Nations said Port-au-Prince's main airport was "fully operational" and open to relief flights.
The U.S. Navy aircraft carrier, USS Carl Vinson, is under way and expected to arrive off the coast of Haiti Thursday. Additional U.S. Navy ships are under way to Haiti, a statement from the Southern Command said.
Aftershocks continued to rattle the capital of 2 million people as women covered in dust clawed out of debris, wailing. Stunned people wandered the streets holding hands. Thousands gathered in public squares to sing hymns.
U.N. humanitarian chief John Holmes said it was possible that the death toll "will be in the thousands."
"Initial reports suggest a high number of casualties and, of course, widespread damage but I don't have any figure that I can give you with any reliability of what the number of casualties will be," Holmes said.