(Corrects weight of equipment to 17,200 pounds/7,800 kg in paragraph 14)
By Jeff Mason and Tom Doggett
WASHINGTON (Reuters) - The United States showed increasing alarm on Wednesday about how Japan was handling its nuclear crisis, urging Americans to leave the area near an earthquake-crippled power plant and relying on U.S. experts for updates.
Without criticizing the Japanese government, which has shown signs of being overwhelmed by the crisis, U.S. officials admitted their call for American citizens to evacuate the area near the Fukushima nuclear plant went further than Japanese advice.
The State Department recommended that U.S. citizens within 50 miles of the Fukushima plant leave the area or stay indoors "if safe evacuation is not practical."
Japan's government has asked people living within 12 miles of the Fukushima plant to evacuate and those between 12 miles and 18 miles to stay indoors
The State Department's warning to U.S. citizens was based on new information collected by the U.S. Nuclear Regulatory Commission, Department of Energy and other U.S. sources.
The top U.S. nuclear regulator told Congress on Wednesday that radiation levels around Japan's troubled nuclear power plant may give emergency workers "lethal doses" of radiation, preventing them from getting near the plant.
"We believe that around the reactor site there are high levels of radiation," said Gregory Jaczko. "It would be very difficult for emergency workers to get near the reactors. The doses they could experience would potentially be lethal doses in a very short period of time."
The U.S. military has also ordered its forces to stay 50 miles away from the plant, the Pentagon said, outlining a larger no-go zone than the one Japan has recommended.
"This is a very serious situation at this nuclear plant," White House spokesman Jay Carney said.
"We are concerned enough that we have offered a great deal of assistance to the Japanese and we have our own experts on the ground both assisting and evaluating information independently for that reason."
Earlier on Wednesday, another fire broke out a the nuclear facility, which has sent low levels of radiation wafting into Tokyo in the past 24 hours.
Carney said President Barack Obama had been briefed about the deteriorating situation.
The United States is trying to deploy equipment in Japan that can detect radiation exposure at the ground level, U.S. Energy Secretary Steven Chu told a congressional hearing.
The detection system is part of the 17,200 pounds (7,800 kg) of equipment and 39 personnel from the Energy Department sent to Japan, Chu said. The department has also provided equipment to monitor airborne radiation.
Chu declined to tell lawmakers, when asked, whether he was satisfied with Japan's response so far to its nuclear crisis.
"I can't really say. I think we hear conflicting reports," Chu said.
"This is one of the reasons why ... (the United States is) ... there with boots on the ground, with detectors in the ground, not only to help assist (the) Japanese power company and the Japanese government but also for our own sake to know what is really happening."
The Obama administration has maintained its support for expanding U.S. use of nuclear energy despite renewed fears about its safety after the events in Japan.
But U.S. Secretary of State Hillary Clinton said on Wednesday that the nuclear crisis raised questions about the use of nuclear energy in the United States.
"What's happening in Japan raises questions about the costs and the risks associated with nuclear power, but we have to answer those. We get 20 percent of our energy right now in the United States from nuclear power," she said in an interview with MSNBC in which she emphasized the need for a comprehensive U.S. energy policy.
(Writing by Jeff Mason; reporting by Ayesha Rascoe, David Morgan and Phil Stewart)