* Most powerful quake in Haiti in 200 years
* Ambassador pleads for world's help
* Haiti ill-equipped to deal with disaster
By Joseph Guyler Delva
PORT-AU-PRINCE, Jan 13 A major earthquake rocked Haiti, killing possibly thousands of people as it toppled the presidential palace and hillside shanties alike and leaving the poor Caribbean nation appealing for international help.
A five-story U.N. building was also brought down Tuesday by the 7.0 magnitude quake, the most powerful to hit Haiti in more than 200 years according to the U.S. Geological Survey.
Reuters television footage from the capital, Port-au-Prince, showed scenes of chaos on the streets with people sobbing and appearing dazed amid the rubble.
The quake's epicenter was only 10 miles (16 km) from Port-au-Prince, which has a population of about 1 million, and aftershocks as powerful as 5.9 rattled the city throughout the night and into Wednesday. Reports on casualties and damage were slow to get out of Haiti due to communication problems.
As the poorest country in the Western Hemisphere, Haiti is ill-equipped to respond to such a disaster.
"I am appealing to the world, especially the United States, to do what they did for us back in 2008 when four hurricanes hit Haiti," Raymond Alcide Joseph, Haiti's ambassador to Washington, said in a CNN interview.
"At that time the U.S. dispatched ... a hospital ship off the coast of Haiti. I hope that will be done again ... and help us in this dire situation that we find ourselves in. I'm asking the Haitians who are abroad to work together and bring all the effort in a concerted manner to help those back home."
Sara Fajardo, a spokeswoman for Catholic Relief Services, told the Los Angeles Times that it's representative in Haiti said the death toll could be in the thousands.
U.S. ORGANIZING RESPONSE
U.S. President Barack Obama said his "thoughts and prayers" were with the people of Haiti and pledged immediate aid. A late-night White House meeting involving various arms of the government was held to coordinate the U.S. response.
The Inter-American Development Bank said it would provide $200,000 in immediate emergency aid. The World Bank, which said its local offices were destroyed but that most staff were accounted for, plans to send a team to help Haiti assess damage and plan a recovery.
The U.S. Coast Guard in Miami said it had mobilized cutters and aircraft to positions close to Haiti to give humanitarian assistance as needed.
French President Nicolas Sarkozy's office said in a statement on Wednesday France was sending rescue services to help operations in Haiti and find French citizens there.
The quake hit at 5 p.m. (2200 GMT), and witnesses reported people screaming "Jesus, Jesus" running into the streets as offices, hotels, houses and shops collapsed. Experts said the quake's epicenter was very shallow at a depth of only 6.2 miles (10 km), which was likely to have magnified the destruction.
The presidential palace lay in ruins, its domes fallen on top of flattened walls. CNN reported on its website that Haitian Ambassador Joseph said President Rene Preval was safe, but gave no further details.
Bloodied and dazed survivors gathered in the open and corpses were pinned by debris.
The United Nations said a large number of its personnel in Haiti were unaccounted for after a five-story building at the headquarters of the U.N. mission collapsed.
"The whole city is in darkness. You have thousands of people sitting in the streets with nowhere to go," said Rachmani Domersant, an operations manager with the Food for the Poor charity. "There are people running, crying, screaming."
LITTLE HELP FOR VICTIMS
In the hillside neighborhood of Petionville, Domersant said he saw no police or rescue vehicles.
"People are trying to dig victims out with flashlights," he said. "I think hundreds of casualties would be a serious understatement."
Witnesses said they saw homes and shanties built on hillsides come tumbling down as the earth shook.
"The car was bouncing off the ground," Domersant said.
U.N. officials said normal communications had been cut off and the only way to talk with people on the ground was via satellite phone. Roads were blocked by rubble.
U.N. peacekeeping chief Alain Le Roy said the main U.N. building in Port-au-Prince had collapsed. "We don't know how many people were in the building," he told reporters.
Some 9,000 U.N. police and troops are stationed there to maintain order and many countries were trying to determine the welfare of their personnel.
France's minister for cooperation, Alain Joyandet, said on French radio the Hotel Montana had collapsed and that about 100 of its 300 guests had been evacuated.
Le Roy's deputy Edmond Mulet said 200 to 250 people worked in the collapsed U.N. building during normal hours.
There were more houses destroyed than standing in Delmas Road, a major thoroughfare in Port-au-Prince, another Food for the Poor employee said.
The Hotel Montana, where many foreigners stay, was also damaged.
(Additional reporting by Alister Bull, Jane Sutton and Phil Barbara; Writing by Pascal Fletcher; Editing by Bill Trott and Alex Richardson) ((email@example.com; +1 305 810-2688))