* No radiation leaked
* Unplanned closure tightens power supply further
* PM Kan aims for stability at Fukushima earlier than planned (Adds comments from PM Kan, nuclear minister)
TOKYO, July 16 (Reuters) - Japan's Kansai Electric Power Co on Saturday shut down one of its reactors due to technical glitches, worsening a tight power supply that is stifling manufacturers.
The No.1 reactor at Kansai's Ohi plant, located 350 km (220 miles) west of Tokyo, was manually closed for checks after pressure in a tank containing boric acid water fell for a time on Friday night for unknown reasons, a company spokesman said.
The pressure has since come back up to the normal range, and no radiation leakage has occurred.
"Power supply (in western Japan) has been quite tight in the first place. This problem at Ohi's No.1 unit is making it worse," Nuclear Minister Goshi Hosono told reporters.
"We want to keep restrictions on economic activities and people's daily lives as little as possible. But it is quite clear that the situation has become very severe now."
The government is already ordering power users in Tokyo and surrounding areas as well as in northern Japan to cut their electricity consumption by 15 percent as safety concerns following a radiation crisis at the Fukushima nuclear plant keep some reactors from restarting after routine maintenance.
Kansai Electric, which serves the major western Japan city of Osaka and its vicinity, has so far been asking its clients only for voluntary reduction of power usage.
Among Kansai's customers are the flagship factories of such electronic companies as Panasonic Corp and Sharp Corp .
The electric utility's two other reactors are scheduled to go into planned maintenance next week, leaving only four of its 11 units up and running.
A 9.0-magnitude quake and tsunami on March 11 knocked out the cooling functions at Tokyo Electric Power's Fukushima Daiichi nuclear power plant, triggering the world's worst atomic disaster since Chernobyl 25 years ago.
Prime Minister Naoto Kan said work to put the Fukushima plant under control has been progressing well and that he aimed to have the "step two" of the process, in which engineers plan to bring the reactors to stability by January, completed earlier than scheduled.
"I told (heads of municipalities in Fukushima) we'll do our utmost so that people can go back to their hometown, and the 'step two' phase will be finished ahead of plan," Kan told reporters.
Tokyo Electric plans to hold a news conference on Tuesday to provide an update its Fukushima-related progress. (Reporting by Kiyoshi Takenaka; Editing by Ron Popeski and Jane Baird)