Iran and Russia are scheduled to sign a contract for the return of spent nuclear fuel to Moscow, in the southern city of Bushehr on Sunday, said an official in Tehran on Saturday.

"The deal includes three documents with two of them relating to to the protocol and financial issues. They will be signed Sunday when Russian top nuclear official Alexander Rumyantsev inspects the Bushehr power plant," Deputy for International Affairs and Planning of Iran's Atomic Energy Organization Mohammad Saeedi told IRNA.

"The third document attached to the deal is related to the setting a date for return of the spent fuel which must be finalized. The debate on the timing for return of the spent fuel would be resolved at earliest time", he added.

He noted, "The Russians should show some flexibility. The issues are to be resolved Saturday night and the deal is to be signed Sunday in Bushehr."

He also noted that the talks between Iranian and Russian officials were making headway, adding that it was agreed to proceed with the second phase of Bushehr power plant.

Both sides underlined that the timing of the first phase of the power plant should be shortened and that the Iranian and Russian experts have to work overtime so that the power plant would become operation ahead of schedule.

Referring to the second working group of Bushehr power plant, he stressed that the group is to prepare a comprehensive report within six months and then the option and the site of the second phase will be discussed later.

Head of the Russian Federal Atomic Energy Agency, Alexander Rumyantsev, heading a delegation, arrived in Tehran late Friday.

Rumyantsev is scheduled to visit Bushehr atomic power plant Sunday.

Rumyantsev and his Iranian counterpart Gholam Reza Aqazadeh held lengthy talks but their press conference was postponed and rescheduled to be held in Bushehr on Sunday, said Saeedi.