U.S. President Barack Obama said Thursday his country is offering 100 million U.S. dollars for emergency assistance for the quake-stricken Haiti, and promised his administration's full support to relief efforts.

"Responding to a disaster of this magnitude will require every element of our national capacity -- our diplomacy and development assistance; the power of our military; and, most importantly, the compassion of our country," he said.

Obama has ordered U.S. agency and department heads to treat Haiti as "top priority for their departments and agencies right now," promising that Haiti "will not be forsaken," "will not be forgotten," and "one of the largest relief efforts in our recent history is moving towards Haiti."

Obama said the first waves of U.S. rescue and relief workers are on the ground and at work. A survey team worked overnight to identify priority areas for assistance, as search and rescue teams began to work on saving lives.

He said the military has secured the airport and prepared it to receive the heavy equipment and resources. An airlift has been set up to deliver high-priority items such as water and medicine.

U.S. military has already sent several Coast Guard cutters to Haiti, providing basic services such as water to vital technical support for logistical operation. According to Obama, elements of the Army's 82nd Airborne Division are due to arrive Thursday. A Marine Expeditionary Unit, the aircraft carrier USS Carl Vinson, and the Navy's hospital ship, the Comfort, are all being deployed.

However, Obama said it will take hours, "in many cases days," to get the full U.S. relief capacity on the ground in Haiti, as roads there are "impassable," main port "badly damaged," communications "just beginning to come online," and aftershocks continue.