The United States is sending military and humanitarian assistance to Japan, after an 8.9-magnitude earthquake and tsunami ravaged the nation on Friday.
Operation Tomodachi, Japanese for "friendship," is coordinating all humanitarian assistance and disaster relief operations.
Although the United States is preparing Marine, Navy and Air Force units to help -- and American experts and humanitarian groups are offering assistance, though they still have to wait for the Japanese to give the green light to assist and specify where and what kind of help is needed.
"We have units from all of our services, with a multitude of capabilities, from medical to communications to civil engineering, poised and ready to support where needed," U.S. Ambassador to Japan John Roos said in a paper statement.
Two Marine helicopters have already delivered 1,500 pounds of rice and bread to the hardest hit area, Shioishi City in Miyagi Prefecture. The food was a donation from Ebina City, a suburb of Tokyo. Meanwhile, five Air Force helicopters and crews from rescue squadrons were en route to an air base near Tokyo to support search and rescue missions.
Eight Navy ships are either nearby, or moving toward Japan. The USS McCampbell and USS Curtis are at sea preparing to help with at-sea search and rescue and recovery operations; they will be joined by the USS Mustin on Sunday.
The USS Ronald Reagan is also expected to arrive on Sunday, functioning as a refueling station for the Japan Self-Defense Forces and helicopters involved in search and rescue.
The USS Blue Ridge was re-stocked with aid, including food and water, and is expected to arrive on Friday. Three more ships, the USS Tortuga, USS Essex and USS Germantown are also en route to Japan.
The Japanese government has accepted help from the U.S. Agency for International Development, which sent search and rescue teams from Fairfax and Los Angeles to assist rescue efforts Saturday morning.
The teams include 150 personnel and 12 dogs trained to detect live victims. They will join Japanese and international search and rescue teams in the search for trapped survivors upon arrival on Sunday morning.
Japan Disaster Relief: U.S. Mobilizes Humanitarian, Military Aid
Two officials from the U.S. Nuclear Regulatory Commission were also on board that USAID flight, though Japan has not yet accepted an offer of assistance from the commission.
"We have some of the most expert people in this field in the world working for the NRC and we stand ready to assist in any way possible," said Chairman Gregory Jaczko in a paper statement.
The American Red Cross has also extended an offer of help. So far, Japanese Red Cross said it would accept financial support to help provide first aid and relief items to those displaced.
American Red Cross will deploy a disaster management expert Sunday from Washington, D.C., for a week-long mission. She will serve on a seven-person, international team focused on providing high-level support and advice.
Across the board, the Japanese continue to lead the local earthquake and tsunami response, while American military units, experts, and humanitarian groups stand by, ready to answer a call for help.
ABC News' Jack Date, Luis Martinez and Kirit Radia contributed to this report.