US Secretary of State Hillary Clinton pledged full support for quake-hit Japan on Sunday as the operator of its stricken nuclear plant said it expects to achieve "cold shutdown" in six to nine months.

Japan's embattled Tokyo Electric Power Company(TEPCO) offered the timeline more than five weeks after a giant quake and tsunami hit the Fukushima Daiichi plant, which has since leaked radiation into the air, soil and sea.

Clinton, on a brief, largely symbolic stop in Tokyo, voiced solidarity and vowed that theUnited States would "do everything we can to support you as you come through this time of trial".

"And we know you will emerge even stronger than before," she said after meeting Foreign Minister Takeaki Matsumoto.

Since the March 11 disaster, US forces stationed in Japan and beyond have launched a round-the-clock relief effort bringing supplies to the battered coast -- dubbed Operation Tomodachi, which means "friend" in Japanese.

Prime Minister Naoto Kan later told Clinton: "We will never forget, and we will keep an enduring memory of the very robust support the United States has provided."

Clinton also highlighted the support of American business leaders and had tea withEmperor Akihito at the Imperial Palace -- an unusual invitation from the monarch to a non-head of state.

Clinton and Matsumoto said they were launching a business partnership to support Japan's reconstruction on its northeastern coast, where 13,778 people have been confirmed dead and more than 14,000 are still missing.

While details were vague, the heads of the US Chamber of Commerce and Japan's business lobby Nippon Keidanren said they would meet on ways that foreign companies can take part in the massive rebuilding.

Washington hopes that the large-scale response can help reshape attitudes in Japan, which has been a staunch US ally for decades, but where many citizens bristle at what they see as American domination.

The United States stations 47,000 troops in Japan under a post-World War II security treaty, often leading to friction with host communities for the military bases, especially on the southern island of Okinawa.

Matsumoto said America's help had enabled Japanese people to "feel secure with the Japan-US alliance, including the US military in Japan".

US helicopters have flown aid missions from an aircraft carrier, marines helped clear the tsunami-ravaged Sendai airport which reopened last week, and thousands of personnel joined a search of the coastline for bodies.

American nuclear experts have also helped with advice on stabilising the tsunami-hitFukushima plant, where the US military has flown in coolants and deployed freshwater barges and fire engines to help douse hot reactors.

TEPCO's chairman Tsunehisa Katsumata said at a press conference that the utility aims to cool reactors and start reducing radiation from the facility within three months.

Within six to nine months, TEPCO said, it expects to achieve "cold shutdowns" of all the six reactors, a stable condition in which temperatures drop and radiation leaks fall dramatically.

TEPCO also said that an initial focus would be on preventing new hydrogen explosions in reactors by injecting nitrogen, and on avoiding further releases of radioactive water into the environment.

Kan called the plan "a small step forward", Kyodo News reported.

Trade and industry minister Banri Kaieda said that the roadmap would help move the nuclear crisis from the emergency phase into a stabilisation phase, but he also prodded TEPCO to move faster than the roadmap suggests.

In the short term, TEPCO said earlier, it would send two US-made remote controlled robots into a reactor building damaged by a hydrogen explosion to gauge radiation and temperature levels.

Further north, in the tsunami-shattered town of Rikuzentakata, survivors celebrated a rite of spring as they seek to move on from the catastrophe that shattered so many lives.

About 200 residents cracked open sake, held barbecues and sang songs at a traditional "hanami" party held under blossoming cherry trees, a symbol in Japan of the fleeting beauty and fragility of life.

Source: AFP Global Edition