Invitations to a Syria peace meeting in Switzerland next month have not been issued as planned because of delays in the formation of an opposition delegation, a Syrian newspaper said Tuesday.

"An official source at the foreign ministry said that invitations to attend the 'Geneva 2' conference were not sent out as planned on December 28th," reported the Al-Watan newspaper, which is close to the Syrian regime.

The source told the newspaper that the delay was "the result of the floundering efforts to form a delegation representing the 'opposition'."

The source said a December 27 deadline had been set for the regime and opposition to submit the names of representatives to the meeting on January 22.

He said the government had submitted the details of its delegation but the opposition had yet to do so.

Syria's foreign ministry declined to comment on the report.

UN Secretary General Ban Ki-moon said last week that invites to the conference would be issued before the end of the year.

The 'Geneva 2' conference, named because it is intended to follow a first peace meeting in Geneva, is to be held in Montreux, a city northeast of Geneva.

After months of delays, a January 22 date for the talks has been set, but doubts remain about whether the conference will go ahead.

The key opposition National Coalition has yet to categorically say it will attend the meeting, and warned recently it would not show up if government war planes continued an aerial campaign in northern Aleppo province that has killed over 500 people.

The opposition also insists that President Bashar al-Assad cannot be part of any transition in Syria, but the regime says Assad's departure from office will not be on the table at the peace talks.

Other questions remain unanswered, including whether Iran will attend the talks.

Tehran is the key regional ally of the Syrian regime, which has said it should be allowed to attend, and the opposition is opposed to it being invited to the talks.

More than 126,000 people have been killed since the beginning of the conflict in Syria in March 2011.