The company at the centre of Japan's nuclear crisis says it hopes to bring the Fukushima Daiichi nuclear plant under control in six to nine months, but cannot say when tens of thousands of people forced to evacuate the area will be able to return home.
In the first indication of how long it will take to stabilise the plant, the Tokyo Electric Power Company [Tepco] revealed on Sunday a two-stage process it hopes will end with the safe "cold shutdown" of the stricken reactors.
Tepco's announcement came as the US secretary of state, Hillary Clinton, arrived in Tokyo to pledge Washington's support for Japan as it recovers from the worst disaster in its postwar history.
"Economically, diplomatically and in so many other ways, Japan is indispensable to global problem-solving," she said. "We are very confident that Japan will recover and will be a very strong economic and global player for years and decades to come."
Clinton pledged steadfast support for Japan in the face of "a multidimensional crisis of unprecedented scope".
Japan and the US announced the creation of a public-private partnership to spearhead reconstruction. "We wish to enhance co-operation between Japan and American businesses," Clinton said.
Tepco officials say the two most urgent tasks are to prevent hydrogen explosions at three of the six reactors, and to secure storage for tens of thousands of tonnes of contaminated water in the turbine buildings.
The firm has been pumping low-level radioactive water into the sea, angering neighbouring China and South Korea.
It says it needs three months to achieve a steady reduction in radiation, and another three to six months to bring levels firmly under control.
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"We will do our utmost to curb the release of radioactive materials by achieving a stable cooling state at the reactors and spent fuel pools," Tepco's chairman, Tsunehisa Katsumata, told reporters.
"The company has been doing its utmost to prevent a worsening of the situation. We have put together a roadmap and will put all our efforts into achieving these goals."
The prime minister, Naoto Kan, welcomed Tepco's roadmap as "a small step forward". Earlier, he said in a newspaper editorial that last month's natural disasters and the nuclear crisis presented Japan with "a precious window of opportunity to secure the 'rebirth of Japan' ".
Tepco says plans to stabilise the plant are subject to "various uncertainties and risks", and cannot give a time frame for the return of evacuees.
The trade minister, Banri Kaieda, suggested some residents would be able to return as soon as the the plant was stabilised.
But Katsumata, who admitted he was considering resigning over the crisis, said only that he hopes people will be able to return "as early as possible".
Tepco is to monitor radiation levels in affected towns and villages once the plant is stabilised and liaise with the government about a possible lifting of the evacuation order.
Pressure has mounted on Tepco and the government to give evacuees an idea of when they might be able to return to their homes. At the weekend, Kan was quoted as suggesting they may have to wait up to 20 years. He later insisted he had been misquoted.
"We would like to present the facts to help the government make a judgment and provide an outlook on when evacuees can go home," Katsumata said.