* Most dangerous chemical materials being shipped out
* Syria gave up toxic arsenal in deal with Russia, U.S.
* Islamist leader calls for end to rebel infighting
* Western-backed opposition postpones vote on peace talks
By Oliver Holmes and Erika Solomon
BEIRUT, Jan 7 (Reuters) - Syria has started moving chemical weapons materials outof the country in a crucial phase of an internationally backed disarmament programme that has been delayed by war and technical problems.
The Organisation for the Prohibition of Chemical Weapons said on Tuesday that "prioritychemical materials" were transported to the port of Latakia and onto a Danish vessel which was now sailing towards international waters.
Syria agreed to abandon its chemical weapons by June under a deal proposed by Russia and agreed with the United States after an Aug. 21 sarin gas attack that Western nations blamed on President Bashar al-Assad's forces. Damascus blames rebels for the attack.
War, bad weather, bureaucracy and technical issues meant a Dec. 31 deadline for the removal of the most deadly toxins from Syria was missed.
The OPCW did not disclose what percentage of Syria's toxic arsenal -- which totals 1,300 tonnes in all -- had been removed but said nine containers of the most dangerouschemical materials were on the Danish cargo vessel.
"The vessel has been accompanied by naval escorts provided by Denmark and Norway, as well as the Syrian Arab Republic," a statement said. "It will remain at sea awaiting the arrival of additional priority chemical materials at the port."
Maritime security was being provided by Chinese, Danish, Norwegian and Russian ships.
Government forces have taken back control of the highway linking Damascus to the coast which is needed to transport the toxins. Rebel were ousted from three towns along the road but activists say convoys moving along it will remain vulnerable to rebel ambushes.
Washington welcomed the removal of chemical materials and said Assad's government appeared to be sticking to the deal.
"Much more needs to be done," State Department spokeswoman Jen Psaki told a news briefing, adding: "We have no reason to believe that the regime has gone back on any aspect of their promise."
On the battlefield, Syria's bloodiest bout of rebel infighting since the war started nearly three years ago prompted the head of an al Qaeda-linked rebel group to called for a ceasefire between opposition factions.
An audio recording from the leader of the powerful Nusra Front, known as Abu Mohammed al-Golani, laid much of the blame for the fighting on an al Qaeda splinter group known as the Islamic State in Iraq and the Levant (ISIL).
While both groups have roots in the global Islamist network and welcome foreign militants, the Nusra Front has cooperated more with other rebel groups and has largely avoided the power struggles that ISIL has faced since wresting control of many opposition-held areas from other groups.
"Many rebel units have committed transgressions, just as the mistaken policies followed by played a prominent role in fuelling the conflict," Golani said.
ISIL has also been fighting in Iraq, where it faces an onslaught by army tanks and artillery around the city of Falluja, whose local leaders have urged the Qaeda-linked militants to leave before being attacked.
ISIL gunmen want to reconquer Iraq's Anbar province in pursuit of their goal of creating a radical Islamic state out of the chaos of neighbouring Syria's civil war.
More than 274 people have been killed in the rebel-on-rebel clashes in Syria since they began on Friday, according to the Syrian Observatory for Human Rights, an opposition monitoring group.
Golani proposed forming an Islamic legal council to resolve feuds among the rebels and called for the militants to return to their shared goal of fighting Assad's forces, as the campaign to oust the Syrian leader nears the end of its third year.
It was not possible to verify the audio statement, but it was posted on a Twitter account used by the Nusra Front.
"This unfortunate situation has pushed us to launch an initiative to save the battlefields from being lost. This will be done by forming an independent legal council by all the (rebel) factions in addition to a ceasefire," Golani said.
Rebel groups, many of them also hardline Islamists, last week launched what appeared to be a series of coordinated strikes against ISIL in northern and eastern Syria after months of increasing tensions with the group, which has alienated many Syrians in rebel-held regions.
In one northwestern region of Syria alone, other rebel groups appear to have killed 34 foreign fighters from ISIL, the Observatory said.
Fighting reignited between ISIL and other groups on Tuesday, the Observatory said. Fifteen died in the town of Rastan, north of the central city of Homs, and in Aleppo rebels took control of a police station where about 100 ISIL fighters had been based. The ISIL fighters surrendered themselves and their weapons to the Nusra Front, it said.
Golani urged rebels not to become divided between foreign and local fighters, arguing that all were needed to launch jihad, or holy war, in the country.
The campaign to topple Assad has degenerated into a civil war with several sectarian and ethnic struggles emerging, as well as the internecine fighting now plaguing the rebels.
Golani urged rebels to exchange prisoners and open roads to all opposition units.
TALKS DECISION DELAYED
Syria's Western-backed opposition in exile postponed until next week a decision on whether to attend talks with Assad's government aimed at ending the conflict, opposition members said on Tuesday.
The National Coalition is facing heavy pressure from Western powers to attend the Jan. 22 talks in Switzerland, seen as the most serious effort yet to find a political solution to the civil war.
It has said it is ready to attend the talks in principle, but says they must lead to Assad's departure - a demand which Damascus has flatly rejected - and has repeatedly stalled on its final decision.
The latest delay came after at least a quarter of the coalition called for its newly re-elected president Ahmad al-Jarba to stand down at a meeting in Turkey and threatened to resign if their demand was not met, sources at the meeting said.
(Additional reporting by Omar Fahmy, Alexander Dziadosz, Doina Chiacu and Dasha Afanasieva; Editing by Giles Elgood and David Stamp)