Washington (CNN) -- Any plans to build a nuclear power plant in an area of the United States prone to earthquakes should be reconsidered in light of the damage to Japanese reactors by last week's earthquake and tsunami, Democratic Rep. Ed Markey of Massachusetts told CNN on Monday.
"We just have to call a time out and examine whether or not those safety features necessary in the future are built into new nuclear power plants in our country," said Markey, who sits on the House committee overseeing nuclear power.
In response, the chairman of the independent Nuclear Regulatory Commission, which regulates U.S. reactors, said the plants were built to withstand earthquakes and other natural disasters.
"All our plants are designed to withstand significant natural phenomena, like earthquakes, tornadoes, and tsunamis," NRC Chairman Gregory Jaczko said at the White House.
Jaczko was invited to brief reporters by White House Press Secretary Jay Carney. He also said there is little chance of radiation from the troubled Japanese reactors affecting the United States.
The design of the Japanese reactors and the nature of the problems there made it "a very low probability that there's any possibility of harmful radiation levels in the United States or in Hawaii or any other U.S. territories" from Japan, he said.
The leaking of radiation from Japan's damaged reactors raised questions about the safety of the 104 non-military U.S. nuclear reactors, which provide 20 percent of the nation's power supply.
On Sunday, a Senate proponent of nuclear energy also called for a temporary halt in building nuclear power plants in the United States until the situation in Japan can be examined.
Sen. Joseph Lieberman, an independent from Connecticut who sits with the Democratic caucus, said on the CBS program "Face the Nation" that the United States should "put the brakes on right now until we understand the ramifications of what's happening in Japan."
Markey sounded a similar call Monday, saying, "Any plant that is being considered for a seismically vulnerable area in the United States should be reconsidered right now."
He also called for ensuring that backup systems for U.S. nuclear plants include sufficient cooling fluids for shutting down reactors and for the government to distribute radiation-blocking potassium iodide to people living within a 20-mile radius of a nuclear plant, as was called for in a 2002 bill he authored.
According to Markey, the Bush administration refused to comply with the law, and now he wants the Obama administration to ensure that "any family within a 20-mile radius of a nuclear power plant in the United States has access to the potassium iodide, especially to protect their children." So far, he said, the administration has declined to take that step.
At the White House briefing, Deputy Energy Secretary Daniel Poneman made clear that nuclear power remains part of U.S. energy policy.
"Seventy percent of the carbon-free electricity in this country comes from nuclear power," said Poneman, who also appeared at Carney's request. "So we do see nuclear power as continuing to play an important role in building a low-carbon future, but be assured that we will take the safety aspect of that as of our paramount concern."
House Majority Leader Eric Cantor of Virginia also said the situation in Japan should not affect the role of nuclear power in U.S. energy policy, noting that he agrees with President Barack Obama on that point.
"This is the result of a tsunami, and the shutdown and what is going on over there with the reactor has a direct causal link with the tsunami, so I do believe that we certainly do want to get to the bottom of it, and if we can learn any lessons from Japan's experience for sure," said Cantor, who has a facility in his district applying for a nuclear power plant license. "But nuclear power is an essential part of the energy mix in this country."
Also Monday, Tony Pietrangelo of the Nuclear Energy Institute, the policy organization of the nuclear energy and technology industry, said U.S. plants are "designed to withstand the most severe seismic events or earthquakes, as well as tsunamis where applicable, and flooding."
"We have rules to deal with station blackout, which is what they are experiencing in Japan," Pietrangelo said, referring to the power loss at the Japanese nuclear plants that affected the function of backup response systems. It was the "one-two" punch of the earthquake and tsunami that caused the problem, as the Japanese reactors withstood the shaking without significant problem, he said.
U.S. plants, Pietrangelo said, "are designed for the seismic events in their area."
"The West Coast plants are designed to higher standards than the Central and Eastern United States," he said. "It is based on a historical look at what has happened in those areas, what soil or rock they sit in. They are very robust. I think, as we have seen in Japan, despite the magnitude of that earthquake, they hold up quite well."
To Markey, though, the problem is that "it's impossible to totally predict all of the different kinds of events which can unfold in these types of circumstances."
"Let's be honest," he added, "none of the experts can be 100% certain what magnitude of an earthquake that can hit."
The United States nuclear reactors operate at 65 plants across the country. In addition, there are dozens of reactors, weapons labs and other nuclear facilities associated with national defense. Most of the civilian plants are located near major population centers.
A new nuclear plant has not been commissioned since the Three Mile Island meltdown in Pennsylvania in 1979, although dozens that were under construction at the time have come on line.
More recently, increased electricity use, a desire to generate homegrown energy and concern over global warming have made carbon-free nuclear power more attractive.
The government has set aside $18 billion for new nuclear plants, and Obama wants to spend an additional $36 billion.
Federal regulators are reviewing 20 applications to build nuclear plants, and several existing facilities have applied to extend their operating licenses.
Perhaps the most vulnerable U.S. plants are the two built on California's Pacific coast near the San Andreas Fault.
Those plants were built to withstand a magnitude-7.5 earthquake, said Robert Alvarez, a nuclear expert at the Institute for Policy Studies and a former senior official at the U.S. Department of Energy.
The San Francisco quake of 1906 measured 8.3, said Alvarez, and Friday's Japanese quake was a massive 8.9.
"I don't think we should renew those operating licenses," he said.
Spokesmen for the utilities that own the California plants, Pacific Gas & Electric and Southern California Edison, said Sunday that the plants are designed to meet the maximum quake projected for their immediate vicinity, which is not thought to exceed a magnitude of 6.5.
According to Pietrangelo of the Nuclear Energy Institute, every two years, U.S. nuclear plants undergo emergency planning exercises run by the Nuclear Regulatory Commission and the Federal Emergency Management Agency.
"We are the gold standard of emergency planning, and other industries have learned from what we do on our stations," Pietrangelo said.
CNNMoney's Steve Hargreaves and CNN's Tom Cohen, Deirdre Walsh and Dana Bash contributed to this story.