The Syrian peace talks planned to take place on January 25 may be delayed since the major powers have not reached an agreement on which opposition groups should be invited to the meeting in Geneva, as there is less than a week to the planned date.
On Monday, United Nations spokesman Farhan Haq hinted at a possible delay of the date of the planned meeting.
"At this stage the UN will proceed with issuing invitations when the countries spearheading the ISSG [International Syria Support Group] process come to an understanding on who among the opposition should be invited," said Haq.
"The objective is, and remains, to get the parties to talks in Geneva by the date of the 25th of January. At the same time, of course there are concerns about arrangements," Haq said.
"We will have to see whether the various parties, the members of the Security Council, whether we can all come to an agreement on the best way forward. If we need to alter our timetable one way or another, we will let you know."
Reaching an agreement on which opposition groups would take part in the meeting stands as an obstacle since the parties in Syria, including the US, Turkey, Saudi Arabia on one side and Russia, Iran, the Syrian regime on the other side, have different stances towards the opposition groups.
Both the US and Russia agree on the need for a solution to the Syrian conflict, but the peace process faces obstacles since they support different parties in Syria.
The US, European powers, Turkey and Saudi Arabia back the leaving of Assad from power and support the moderate opposition groups fighting against the regime. Russia and Iran on the other hand have been strong allies of Assad to whom they provide help, including financial aid and weapons.
Moreover, Western and Turkey-Saudi Arabia backed opposition groups fighting against the Bashar al Assad regime in Syria have already said they would not attend the meeting before the regime ends its siege of Madaya.
The Syrian regime has been laying siege to several towns where thousands of civilians are starving to death, a practice many international figures call a war crime.
On Monday the UN announced that humanitarian aid deliveries continued to the Syrian towns of Madaya, Zabadani, Foua and Kafraya. However, reports indicate that there are still thousands are in need of basic necessities such as water.
On December 18, the United Nations Security Council adopted a resolution drawing an international roadmap for a political transition to end the conflict in Syria. The resolution was adopted unanimously, a rare event in the council which consists of rival powers - the US, Russia, China, France, the UK.
According to the UN more than 250,000 people have been killed since the beginning of the conflict. However, the Syrian Observatory for Human Rights (SOHR) puts the number at more than 350,000.