The U.S. military rerouted several ships toward Japan on Friday and began preparing for humanitarian missions in the wake of a devastating earthquake and tsunami that left at least hundreds dead.

Private U.S. aid groups began collecting funds and, in some cases, preparing emergency supplies. But experts said Japan probably would not need the kind of massive support that poor countries such as Haiti require after a crisis. Japan has one of the best government disaster-response agencies in the world, with long experience in recovery from earthquakes.

Still, President Obama said he told Japanese Prime Minister Naoto Kan the United States was ready to help.

“This is a potentially catastrophic disaster, and the images of destruction and flooding coming out of Japan are simply heartbreaking,” Obama said at a news conference.

He said the main U.S. assistance would probably be “lift capacity,” a reference to helicopters and planes that can carry heavy loads.

One of the most urgent needs was digging people out from under crushed buildings. About 70 search-and-rescue teams were on standby around the world awaiting Japan’s request, according to Nicholas Reader of the U.N. Office for the Coordination of Humanitarian Affairs.

The U.S. Agency for International Development dispatched a small assessment team to Japan, and charitable groups also prepared to send representatives to see how they could contribute.