WASHINGTON — President Barack Obama on Wednesday promised an all-out rescue and humanitarian effort to help the people of Haiti overcome a "cruel and incomprehensible" tragedy, the ruinous earthquake that ravaged the poorest country in the Western Hemisphere.

The president said the relief effort is gearing up even as the U.S. government is working to account for Americans who were on the island nation when the disaster struck late Tuesday afternoon.

The State Department Operations Center has set up the following number for Americans seeking information about family members in Haiti: 1-888-407-4747.

Obama said he named U.S. Agency for International Development administrator Rajiv Shah to coordinate American efforts, and the president called upon all nations to join in helping stricken Haitians.

Obama spoke Wednesday in the White House Diplomatic Reception Room. Later, spokesman Robert Gibbs told reporters the president had no plans to go to Haiti.

The president, who has been involved in ensuring a quick response since Tuesday night, said in a statement from the White House Diplomatic Reception Room that one of the government's top priorities is to quickly locate U.S. embassy employees and their families, as well as all other American citizens living and working in Haiti.  

The president received updates on the situation in Haiti and the U.S. response Wednesday morning from his national security adviser and the Department of Homeland Security.

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.

N.C. residents shaken, safe

At least 20 North Carolina residents from Raleigh, Durham and Roanoke Rapids were in Haiti Tuesday and experienced a 7.0-magnitude tremor – the strongest earthquake to hit the poor Caribbean nation in more than 200 years.

Three women from First Christian Church in Roanoke Rapids were on a mission trip with Lifeline Christian Mission when the quake hit. A group leader named Gretchen has been e-mailing updates about their condition.

All members are accounted for, she said, but some have been injured. Most of the injuries were believed to be minor, but one woman might have suffered broken ribs when a piece of a wall fell on her.

"This is a major disaster. All of our cement block walls are down and most of the contents within our buildings were knocked over and thrown across the rooms," Gretchen wrote. "The women are troopers. They are hanging in and only a couple are really scared; some are talking about coming home but where we are is the safest place right now."

Three women from King's Park International Church in Durham and another from Raleigh landed in Haiti about an hour before the earthquake.

Jim Brackett said his daughter, Kellee Metty, contacted him on Wednesday to let him know that she and her three friends were safe.

For Metty, Haiti is a second home. She met her husband there and has continued to go back on mission trips.

“They’ve just had a heart for missions and Haiti,” Metty’s mother, Janice Brackett, said Wednesday.

Metty organized this latest trip with two of her friends from King's Park International Church in Durham, Linda Graham and Lisa Lewis. Metty's dentist in Raleigh, Julia Zervos, also went.

They traveling to help the Christianville Foundation orphanage.

“I always am a little apprehensive when she goes off on one of her treks somewhere and I just said, ‘Be careful,’” Janice Brackett said.

A member of Horne Memorial United Methodist Church in Clayton who is on her 43rd mission trip to Haiti has said in an e-mail that she and the five others in her team are safe.

Helen Little, 77, traveled to Haiti with Linda Mitchell and Joan Gregg from Epworth UMC in Durham and Darlene Lee, Steve Wales and Ann Collier from Whitley Memorial in Smithfield.

The Rev. Dr. Sam Dixon, a clergy member of the North Carolina Conference of the United Methodist Church and head of the United Methodist Committee on Relief, is also in Haiti. Officials said he was on his way to the airport in Port-Au-Prince when the earthquake occurred. He has not been heard from.

Gwen Whiteman works with the local office of Hearts with Haiti, a Cincinnati-based charity group that runs three homes for poor and disabled children in the island nation.

The earthquake damaged two of the homes and destroyed the third.

Whiteman said the children and founder are safe, but a staffer was hurt.

“We're very worried about him and eagerly awaiting word that he's going to be alright,” Whiteman said.

Thousands feared dead

Officials feared thousands - perhaps more than 100,000 - may have perished in the earthquake but there was no firm count.

President Rene Preval said he believes thousands were killed in Tuesday afternoon's magnitude-7.0 quake, and the scope of the destruction prompted other officials to give even higher estimates.

Leading Sen. Youri Latortue told The Associated Press that 500,000 could be dead, although he acknowledged that nobody really knows.

"Parliament has collapsed. The tax office has collapsed. Schools have collapsed. Hospitals have collapsed," Preval told the Miami Herald. "There are a lot of schools that have a lot of dead people in them."

Even the main prison in the capital fell down, "and there are reports of escaped inmates," U.N. humanitarian spokeswoman Elisabeth Byrs said in Geneva.

The head of the U.N. peacekeeping mission was missing and the Roman Catholic archbishop of Port-au-Prince was dead.

"The cathedral, the archbishop's office, all the big churches, the seminaries have been reduced to rubble," Archbishop Bernardito Auza, the apostolic envoy to Haiti, told the Vatican news agency FIDES.

The parking lot of the Hotel Villa Creole was a triage center. People sat with injuries and growing infections by the side of rubble-strewn roads, hoping that doctors and aid would come.

The international Red Cross said a third of Haiti's 9 million people may need emergency aid and that it would take a day or two for a clear picture of the damage to emerge.

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.