DAMASCUS, Dec. 28 -- The joint OPCW-UN mission in Syria said Saturday that the transportation of the most critical chemical material out of Syria before the deadline of December 31, 2013 is unlikely due to the volatility in overall security conditions in Syria.

In a statement issued Saturday, the joint mission of the Organization for the Prohibition of Chemical Weapons (OPCW) and the United Nations (UN) said "Preparations continue in readiness for the transport of most of the critical chemical material from the Syrian Arab Republic for outside destruction. However, at this stage, transportation of the most critical chemical material before December 31 is unlikely."

While announcing a delay in moving the chemical material out of Syria, the statement said a number of external factors have impacted upon timelines.

It also said that the Syrian government has also indicated its specific requirements, which it deems critical to the package and transport of chemical weapons material, adding that a wide-scale procurement effort by individual member states of the Security Council has been facilitated by the OPCW-UN Joint Mission to source, collect and deliver various packaging and transport materials requested by Syria.

"Logistical challenges coupled with inclement weather have contributed to this delay," the statement said.

It said preparations are well advanced in regards to the supply of materials and transport equipment, as well as the provision for the maritime transport and destruction capabilities, in order to commence removal and transport of most the critical chemical material from Syrian territory as soon as possible.

Removing the critical chemical material from Syria is a second stage after the OPCW-UN Joint Mission confirmed that the Syrian government had completed the destruction of all unfilled chemical munitions well ahead of the timeline set by the OPCW Executive Council.

In spite of the volatile situation in Syria and the significant challenges ahead, the OPCW-UN Special Coordinator Sigrid Kaag called upon all parties in Syrian conflict to ensure the timely removal and continued destruction of Syrian declared chemical weapon program, according to the statement.

The United Nations Security Council and OPCW Executive Council established timelines for the removal and elimination of Syrian chemical weapons program by the end of June 2014, following the Syrian government approval to destroy its chemical arsenal recently.

The chemical materials were set to be shipped outside the country via Syria's coastal city of Latakia to be destroyed on a ship in the sea. Russia has reportedly sent special vehicles to help the government of Syria transporting the materials from different parts of the country to Latakia.

Last week, Syria's Foreign Ministry said that government forces had repelled a series of rebel attacks on sites where chemical weapons are held.

Armed groups reportedly used vehicles equipped with heavy machine-guns during the assaults in central and southern areas of the country.

The foreign ministry said the attacks were carried out by the al-Qaida-linked Nusra Front, and the so-called Islam Brigade, accusing the rebels' regional patrons of providing the jihadists on ground with the coordinates of the weapons' locations.