Akhir 12, 1432 H/March 17, 2011, SPA -- U.S. President Barack Obama believes that Japan is fully aware of the severity of the nuclear crisis it is facing, Reuters quoted White House spokesman Jay Carney as saying on Thursday. The United States has recommended its citizens to stay further from a stricken Japanese nuclear plant than the Japanese government has recommended, prompting concerns that the two allies differed on the seriousness of the situation.