President Obama offered his condolences to the Japanese people today and said the United States is monitoring the situation in Asia and its own shores closely.
"Today's events remind us of just how fragile life can be," the president said. "Our hearts go out to our friends in Japan and across the region, and we're going to stand with them as they recover and rebuild from this tragedy."
The president said the United States has mobilized efforts, including ship and air power to assist the Japanese. The United States has one aircraft in Japan and another is on the way, and a ship is also en route to Marianas Islands for assistance, Obama said.
The State Department is working to account for and assist all American citizens in the country, he said.
The president also warned Americans in tsunami prone areas to heed all warnings.
"Here in the United States there hasn't been any major damage so far, but we're taking this very seriously, and we are monitoring the situation very closely," he said. "FEMA is fully activated and is coordinating with state and local officials to support these regions as necessary."
"And let me just stress that if people are told to evacuate, do as you are told," he added.
Obama called Japanese Prime Minister Naoto Kan earlier this morning to discuss the situation, and was later briefed by his national security team.
When asked for his personal assessment on the strategy, Obama said he was "heartbroken" by the images streaming on television.
"I think when you see what's happening in Japan, you are reminded that, for all our differences in culture or language or religion, that ultimately humanity is one," he said. "And when we face these kinds of natural disasters, whether it's in New Zealand or Haiti or Japan, then you think about your own family, and you think, how would you feel if you lost a loved one, or if your entire life savings were gone because of the devastation?"
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The United States quickly mobilized efforts and redirected its assets in the region to aid the Japanese shortly after the devastating 8.9 magnitude earthquake and tsunami shook the country, even though a formal request didn't come until much later.
A USAID Disaster Assistance Response Team is assembling to go to Japan, with their team leader already en route, USAID spokesman Lars Anderson told ABC News. USAID has stood up a Response Management Team in its Washington, D.C. headquarters to oversee logistics of a U.S. response.
A Defense Department official said U.S. Pacific Command is sending some P-3 Orion maritime surveillance aircraft to support the Japanese government by providing aerial reconnaissance over quake-damaged areas.
The amphibious assault ship USS Essex and its Marines aboard are set to depart Malaysia for Japan.
A Defense Department official said the aircraft carrier USS Ronald Reagan is being moved to Japan in case it is needed for helicopter support. The carrier had just arrived in the region to participate in an annual exercise with South Korea.
Japan is one of the United States' closest allies in the region, and the two countries routinely conduct joint military exercises. The U.S. Navy has a large presence in Japan, which is home to U.S. Seventh Fleet Headquarters and the aircraft carrier USS George Washington.
The United States maintains several large bases in Japan with 38,000 military personnel, 43,000 dependents and 5,000 Department of Defense civilians.
ABC News' Luis Martinez, Jake Tapper, Kirit Radia and Martha Raddatz contributed to this report.