Akhir 12, 1432 H/March 17, 2011, SPA -- The United States has authorized the first evacuations of Americans out of Japan, taking a tougher stand on the deepening nuclear crisis and warning U.S. citizens to defer all non-essential travel to any part of the country, AP reported. The U.S. worried that unpredictable weather and wind conditions risked spreading radioactive contamination. The U.S. is doing minute-by-minute analysis of the fast-moving situation, Secretary of State Hillary Rodham Clinton said Thursday. President Barack Obama placed a telephone call to Prime Minister Naoto Kan on Wednesday to discuss Japan's efforts to recover from last week's devastating earthquake and tsunami, and the nuclear crisis at the Fukushima Dai-chi plant. Obama promised Kan that the U.S. would offer constant support for its close friend and ally, and «expressed his extraordinary admiration for the character and resolve of the Japanese people,» the White House said. But a hastily organized teleconference late Wednesday with officials from the State and Energy Departments underscored the administration's concerns. The travel warning extends to U.S. citizens already in Japan and urges them to consider leaving. The authorized departure offers voluntary evacuation to family members and dependents of U.S. personnel in Tokyo, Yokohama and Nagoya and affects some 600 people. Senior State Department official Patrick Kennedy said chartered planes will be brought in to help private American citizens wishing to leave. People face less risk in southern Japan, but changing weather and wind conditions could raise radiation levels elsewhere in the coming days, he said. «This is a very serious problem with widespread ramifications,» Clinton said during a visit to Tunisia. «There will be a continuing evaluation. This is ... a minute-by-minute analysis and we're doing everything we can to support the Japanese and their heroic efforts in dealing with this unfolding disaster.» Pentagon spokesman Col. Dave Lapan said the military will coordinate departures for eligible Defense Department dependents. The decision to begin evacuations mirrors moves by countries such as Australia and Germany, who also advised their citizens to consider leaving Tokyo and other earthquake-affected areas. Tokyo, which is about 170 miles (270 kilometers) from the stricken nuclear complex, has reported slightly elevated radiation levels, though Japanese officials have said the increase was too small to threaten the 39 million people in and around the capital. -- SPA