The White House announced today that U.S. citizens living within a 50 mile radius of the nuclear plant in Japan that may be melting down should evacuate the area as soon as possible, even though Japan has only set a 20 kilometer radius which is about 12 miles. It's the first sign of a split between the U.S. and Japan on nuclear advisories since last week's earthquake and tsunami.

White House reporters pounced on White House Press Secretary Jay Carney, wondering why the U.S. had not previously made this request and questioning whether the White House and U.S. government are receiving all the information needed from Japan to keep U.S. citizens safe.

Carney says the new advisory is based on information received just today by the head of the Nuclear Regulatory Commission and does not undercut the advice the Japanese government has provided to its people - it's just how the U.S. would handle the situation if it happened in America.

"Based on our analysis, this is what we would do if this incident were happening in the United States and because we have U.S. citizens in Japan, this is the advise that we're giving American citizens," Carney said. "It is a separate analysis based on American standards the NRC has and the advice they would give."

But reporters at the White House pressed Carney, saying the new advice by the NRC clearly undermines the government in Japan and suggests that Japanese citizens who don't evacuate outside a 50 mile radius would be taking a risk.

"That recommendation suggests the advice the Japanese government is giving, based on the information it has, is different from the advice we would be giving if it were happening in the United States of America," Carney said.

Carney said the U.S. has offered help and assistance to both U.S. citizens in Japan who may want to leave, and has also offered aid to the Japanese government. But he made clear, that unlike other foreign governments, the United States is not calling for all Americans to evacuate the country.