"This is one of those moments that calls out for American leadership," he said at the White House. "One of the largest relief efforts in our recent history" is …

… now en route to Haiti.

Several elements of the U.S. military have already been dispatched to the stricken Caribbean country and ensured its airport is operating, he added. The "first waves" of U.S. rescue and relief workers are "on the ground and at work."

Among other things, he said, an airlift of water and medical supplies has been set up.

But roads in Haiti are still impassable, the country's main port is badly damaged, and its communications network is just starting to come back on line, he said.

"To the people of Haiti, we say clearly and with conviction, you will not be forsaken," he declared. "You will not be forgotten. In this, your hour of greatest need, America stands with you. The world stands with you."Obama was surrounded by several high-ranking administration officials - including Vice President Joe Biden, Defense Secretary Robert Gates and Secretary of State Hillary Clinton - as he made his remarks.

The president said he had "made it clear" to his national security team that Haitian relief efforts must be "a top priority for their departments and agencies right now."

Obama promised that the United States will partner with other countries, non-governmental organizations and the United Nations in coordinating relief efforts. He also said the U.S. government "will not rest" until all Americans in Haiti are accounted for.

"There is "no higher priority than the safety of American citizens," he said. The U.S. government has already airlifted several injured Americans out of Haiti, and additional evacuations will be conducted in the days ahead, he noted.

"For the sake of our citizens who are in Haiti, for the sake of the Haitian people who have suffered so much, and for the sake of our common humanity, we stand in solidarity with our neighbors to the south, knowing that but for the grace of God there we go," he said.

***