DEVISTATION IN HAITI....

Thousands are trapped, missing or feared dead a day after Haiti's devastating 7.0-magnitude earthquake, prompting the U.N. chief to plead Wednesday for the world to "come to Haiti's aid in this hour of need."

The death toll is difficult to measure, but The Red Cross reports as many as three million people were affected by the disaster, which left the capital city of Port-au-Prince in shambles. Grim scenes played out in the streets, with injured survivors pleading for help and stacking up bodies of the dead.

Dr. Louis-Gerard Gilles, a former Haitian senator, said the poor Caribbean nation is desperate for help.

"The hospitals cannot handle all these victims," he said.

Thousands are trapped in the wreckage of collapsed buildings, which include the presidential palace, a major hospital and a five-story United Nations building. France's foreign minister said its U.N. mission chief in Haiti appears to have died in the quake.

Haiti's ambassador to the United States, Raymond Joseph, told CNN the country's president and his wife are safe, but that the first lady told him "most of Port-au-Prince is destroyed."

There may be more loss of life among the U.N. staff in Haiti, but Alain Le Roy, the chief of U.N. peacekeeping forces, told The Associated Press the organization "cannot give figures for the time being." He said those still unaccounted for include the head of the U.N. mission in Haiti.

U,N. Secretary-General Ban Ki-Moon urged "all members of the international community to come to Haiti's aid in this hour of need."

"There is no doubt we are facing a major humanitarian emergency and that a major relief effort will be required," he said at a news conference in New York.

International rescue and relief teams are mobilizing to respond to the S.O.S., with the U.S. pledging its full support. Venezuela, Mexico, France and Italy are also sending rescue workers, medical supplies, drinking water and canned foods.

U.S. Coast Guard planes are assessing the damage from the air to determine if it is safe for rescue crews to touch down. "We will be providing both civilian and military disaster relief and humanitarian assistance," said Secretary of State Hillary Clinton.

In a statement, President Barack Obama said "we stand ready to assist the people of Haiti."

American medical staff were being recalled to the United States Naval Ship Comfort, a hospital vessel, which plans to depart Baltimore for Haiti later Wednesday.

"The United States is going to do all we can to help," Adm. Michael Mullen, Chairman of the Joint Chiefs of Staff, said Wednesday at a news conference.

The State Department said it was "still in the early stages" of contacting American citizens in Haiti, as the Haitian American community anxiously awaits word on missing relatives. Some are relying on a State Department hotline, as communication to the island has largely been limited due to damaged telephone lines.

Missionaries working in Haiti before the quake struck now join the nation's residents in need.

Louise Ivers, clinical director of the aid organization, Partners in Health, appealed for help in an emotional email to her colleagues, writing, "Port-au-Prince is devastated, lot of deaths.

Temporary field hospital by us... needs supplies, pain meds, bandages. Please help us."