By Jeff Mason and Paul Eckert
WASHINGTON (Reuters) - The United States would like more information from Japan on its nuclear crisis and does not expect harmful radiation from stricken Japanese reactors to reach U.S. territory, officials said on Thursday.
Nuclear Regulatory Commission chairman Gregory Jaczko said the United States was working to provide ideas and possibly equipment to help Japan cool its overheating Daiichi nuclear power plant about 240 km (150 miles) north of Tokyo.
President Barack Obama, who is leaving for a trip to South America on Friday, stopped by the Japanese embassy in Washington to sign a condolence book and said his administration felt "great urgency" to help Japan.
The president is expected to make a fuller statement at 3:30 p.m. EST about the crisis.
The White House said Obama was confident that Japan was aware of the severity of the crisis it faced.
It is sending charter planes to evacuate U.S. citizens from Japan and recommended its citizens stay further from the earthquake-shattered plant than the Japanese government has recommended, prompting concerns that the two allies differed on the seriousness of the situation.
The State Department recommended that U.S. citizens within 50 miles of the plant leave the area or stay indoors.
Japan's government has asked people living within 12 miles to evacuate and those between 12 miles and 18 miles to stay indoors.
The Pentagon announced plans for a voluntary evacuation of U.S. military families from Japan's Honshu island amid growing anxiety about radiation leaking from the nuclear power plant.
Pentagon spokesman Colonel Dave Lapan said the order would apply to thousands of dependents of U.S. military personnel at bases on Japan's biggest island, a massive undertaking that could involve the use of military aircraft if needed.
A spokesman for U.S. forces in Japan estimated that around 20,000 dependents would be eligible.
Officials said it was prudent, based on the evidence, to recommend Americans stay clear of the plant and said, without directly criticizing a seemingly overwhelmed Japanese government, that more information would be helpful.
"We Americans always want more information," Deputy Energy Secretary Daniel Poneman told reporters.
Jaczko reiterated that regulators did not expect the United States to suffer from dangerous radiation resulting from the Japan crisis.
"We don't see any concern for radiation levels that could be harmful here in the United States or any of the U.S. territories," he said.
The State Department said the first U.S. chartered aircraft has left Japan with about 100 people aboard headed for Taiwan and another flight was anticipated on Friday.
(Additional reporting by Andrew Quinn, Phil Stewart, Patricia Zengerle and Emily Stephenson; editing by Anthony Boadle)