ATHENS (Reuters) - A blackout swept Athens a month before the Olympics Monday, but the government brushed off the hour-long disruption as a mere glitch and said there was more than enough electricity to power the summer Games.

Trains, trolley buses and the underground metro system ground to a halt between 1 p.m. and 2 p.m., while traffic lights went out briefly on some main roads.

The city's fire department received more than 500 calls to rescue people trapped in lifts. Power returned to more than 90 percent of Athens by early evening. The blackout scuttled plans for what was meant to be a triumphant first full trial of the new rail line connecting Athens airport to the city center. The train stopped mid-journey and Transport Minister Michael Liapis and accompanying journalists had to walk through tunnels to the nearest station.

"There is enough power for all the country's needs, both now and during the Games," reassured Development Minister Dimitris Sioufas at a news conference.

"The blackout was not due to an electricity shortage, but to miscalculations in managing the system's high voltage."

He did not say what steps would be taken to prevent a similar error during the Games, but Games organizers said even if there were a repeat of Monday's incident it would not affect the competition.

"This system is designed to allow the continuous supply of power for systems including results, scoring, lighting, information technology and television broadcast," the Athens 2004 Organizing Committee (ATHOC) said.

"As such, a similar incident would not affect the competition schedule and broadcasting of the Games."

Greek authorities have assured the International Olympic Committee all steps have been taken to tackle increased power consumption and potential sabotage of the country's power grid.

During the August 13-29 Games all Olympic venues will have an uninterrupted power supply, and any system failures will be fixed in seconds, Sioufas said.

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