Israel opened the Nahal Oz crossing in central Gaza to allow fuel into the Hamas-controlled coastal strip, but power plant officials said the private Israeli fuel company Dor Alon has yet to deliver any fuel.
Palestinian officials said a European Union aid program, which funds fuel for the plant, has not sent its monitors to the crossing to facilitate the shipment as required.
An EU diplomat said an assessment of the funding program was being made and a decision was likely on Monday.
Dor Alon had no immediate comment, but officials said the supplier was delaying the shipment because it was unclear who would pay for it.
About half of Gaza's 1.5 million residents will be affected by the power plant's blackout, power plant officials said.
Israel stopped fuel shipments through Nahal Oz late last week citing security threats.
Israeli Infrastructure Minister Binyamin Ben-Eliezer said the decision to resume deliveries was for Dor Alon to make.
"This is a private company that probably received a security warning from the Defence Ministry. That is why, and rightfully so, the fuel shipments were halted. I assume fuel will start flowing again in a day or two," Ben-Eliezer said.
Ben-Eliezer said that Israel, which supplies 70 percent of Gaza's electricity, was in the process of adding a new power line into the territory.
Israel supplies most of Gaza's electricity as part of past interim peace deals.
According to Palestinian and Israeli officials, Gaza's population uses approximately 200 megawatts of electricity, out of which 120 are provided directly from Israeli power lines, 17 are delivered from Egypt, and 65 are produced at the Gaza plant.
Hanan Greenberg contributed to this report