The company supplying most of the electricity to the Gaza Strip says it will be forced to cut power Friday.
Gaza Generating Company chairman Rafik Malikha says Israel's closing of a border crossing has prevented fuel shipments for the past two days.
All fuel deliveries come from Israel through the Nahal Oz crossing, which Malikha said had closed for security reasons.
Only one of the company's four generators will be able to continue generating electricity until Sunday, when Malikha said all of the company's fuel stocks would be exhausted.
His company runs the only power plant in the Gaza Strip, but some electricity is also supplied by Egypt and Israel's electric company.
After the Hamas faction seized control of the Gaza Strip in June, Israel briefly shut all border crossings, but partially reopened them after U.N. aid agencies warned that Gaza was in danger of food shortages.
Some information for this report was provided by AFP, AP and Reuters.