A rise in radiation halted the clean-up of radioactive water at Japan's Fukushima nuclear power station on Saturday hours after it got under way, a fresh setback to efforts to restore control over the quake-stricken plant.       

The power plant has been leaking radiation into the atmosphere ever since the March 11 quake and tsunami and both China and South Korea have expressed concern over the possibility of further leaks into the sea.       

Tokyo Electric Power Company, the operator of the Fukushima Daiichi plant, said it expected to resume the clean-up within a week.

The plan hit a new hurdle as Japan marked 100 days since the earthquake and tsunami left nearly 24,000 dead or missing and knocked out cooling systems at the plant. Buddhist memorial services were held throughout the country on the day when the bereaved traditionally seek closure from grief.       

A statement issued by the utility, known as TEPCO, said the suspension was prompted by a faster than expected rise in radiation in a part of the system intended to absorb cesium.       

"At the moment, we haven't specified the reason," a TEPCO spokesman told a news conference. "So we can't say when we can resume the operation. But I'd say it's not something that would take weeks."       

The official said teams working at the plant believed the radiation rise could be linked either to sludge flowing into the machinery absorbing cesium or a monitoring error caused by nearby pipes carrying contaminated water.       

But a resumption, he said, was critical to deal with the highly radioactive water. Officials say 110,000 tons, the equivalent of 40 Olympic swimming pools - is stored at the plant, 240 km (150 miles) northeast of Tokyo.        

"Unless we can resume the operation within a week, we will have problems in disposing of the contaminated water," the official said.       

"But if this is caused by the reasons we are thinking, we can resume the operation within a week."       

The official said TEPCO for the moment foresaw no delay in its overall plan to bring the Fukushima Daiichi plant fully under control by the end of the year.       

The plan, derided by some critics as too optimistic, calls for a shutdown of its three unstable reactors by January 2012.        

Storing Contaminated Water       

The company is fighting against time as the plant is running out of places to store the contaminated water. Amounts quickly accumulate as the company pumps in vast supplies to cool three reactors that went into meltdown after the tsunami disabled cooling systems.       

The cleanup operation is one of many steps to stabilize the reactors. It got under way only late on Friday after being delayed by a series of glitches.       

Trade Minister Banri Kaieda, addressing a news conference, said he had told TEPCO to resume the cleanup operation while upholding safety standards, but set no deadlines.       

He said government inspections showed all nuclear power plants in Japan had adequate safety measures against severe accidents and called on local governments to give the green light to restarting reactors.       

Routine maintenance and public concern since the Fukushima accident have left only 19 of 54 reactors still functioning.       

"Power shortages are a big problem for the economy. I would like to seek the understanding of people who live near plants so we can restart power plants that are confirmed to be safe," he said.       

Nuclear operators always seek local government approval in recognition of the importance of support from residents near the plant - though such backing is not legally required.       

Opposition to nuclear power is growing, with one survey this week saying three-quarters of Japanese voters wanting to see a gradual phase out of nuclear power.       

The crisis has prompted the government to go back to "scratch" in considering the future of nuclear power.       

Mainichi Shimbun reported on Saturday that Kunio Hiramatsu, mayor of Osaka, Japan's second largest city, said he would make a proposal to Kansai Electric Power, of which the city is a top shareholder, that the company eventually phase out nuclear power.