The operator of the crippled Fukushima No. 1 nuclear power plant said Thursday it has given up on a plan to begin retrieving debris that contains melted nuclear fuel at the facility's Unit 2 reactor by March, due to technical difficulties.

Tokyo Electric Power Company Holdings (Tepco) now aims to start the process by October this year at the plant, where reactors were severely damaged by the loss of cooling functions triggered by the Great East Japan Earthquake and tsunami in 2011.

Retrieving the highly radioactive mixture of melted nuclear fuel and debris from the crippled power plant is considered one of the hardest tasks in the process of its decommissioning.