CEYLANPINAR, TURKEY // A ceasefire agreement that ended three months of fighting between Arab rebel groups and Kurdish militants in Syria's north-east is unlikely to hold, experts say.
The two sides have been fighting in Ras Al Ayn since last November, when Turkey assisted Arab fighters opposed to the Syrian president, Bashar Al Assad, to enter the town and engage militants of the Kurdish Democratic Union Party (PYD).
The Arab fighters and PYD signed a deal to end the fighting at the weekend.
The PYD is considered the Syrian branch of the Kurdistan Workers' Party (PKK), which has fought a decades-long war with Turkey.
According to Cengiz Candar, a Turkish commentator and Middle East expert, Turkey's logistical support for the Arab rebels was a signal of its displeasure with the Kurdish militants on its border.
"It will not stand by as another Kurdistan may appear at its door under the control of PKK-guided elements," he said.
The Arab rebels and PYD fighters engaged in sustained clashes after forces loyal to Mr Al Assad withdrew, according to officials and residents in Ceylanpinar, just across the border from Ras Al Ayn.
Over 10 days in late January, 172 wounded Arabs were brought to the Ceylanpinar hospital and an ambulance was always ready at the border, said a municipal official in the Turkish town.
With the towns separated only by train tracks and razor wire, several Ceylanpinar residents were wounded by frequent cross-border fire.
Arab fighters freely crossed into Ceylanpinar for food and supplies, with The National encountering a group of them at a local gun shop.
However, Ankara's talks with the PKK's jailed leader Abdullah Ocalan earlier this year, and diplomatic efforts by Syria's political opposition created pressure for a deal to end the fighting.
"I think the Syrian opposition coalition and the Turks realised that they needed to defuse this tinderbox," said Joshua Landis, a Syria expert at Oklahoma State University.
Turkey's support for the Arab rebels was also called into question because of the presence of groups with links to Al Qaeda, such as Al Nusra Front and Ghuraba Al Sham, leading the fighting. The US designated Al Nusra Front a terrorist organisation last year.
Western countries are terrified of the resurgence of Al Qaeda in Syria, Mr Landis said.
"Yet Turkey is aiding and abetting," he said. The fighting in Ras Al Ayn had revealed Turkey's "shortsighted" policy of acting as "thoroughfare" for Islamist militants travelling to Syria, he said.
While the freedom of movement given to Arab anti-regime fighters appears part of a standard policy, the Turkish prime minister, Recep Tayyip Erdogan, earlier this month took the unusual step of praising rebels in Ras Al Ayn for starting "to squeeze the PYD", according to the Hurriyet newspaper.
However, as fighting reached a stalemate and Ankara's negotiations with Ocalan moved forward, one of the leaders of the Arab militants fighting the PYD resigned early this month for reasons he refused to explain.
Only weeks before, Sheikh Nawaf Bashir, who is accused of receiving financial backing from Turkey, had claimed to be leading "Syrian people" against the PYD, who he accused of collaborating with the Al Assad regime.
"If Turkey reaches a compromise with Ocalan … it will have a bearing on Kurds in Syria and it will have a bearing on the PYD as well," Mr Candar said.
At the beginning of February, the independent Syrian dissident Michel Kilo, a Christian, stepped in to mediate a ceasefire. Both Kurds and Arabs had demanded the Syrian political opposition negotiate a settlement.
Mr Kilo said that the mainstream Free Syrian Army (FSA) signed the agreement on behalf of all rebel groups except Al Nusra Front. "Still, Al Nusra took part in the talks and guarantees the agreement will not be broken," he said.
After the agreement had been signed, [Arab fighters] started to leave Ras Al Ayn moving towards the interior of Syria, said Newaf Khalil, a spokesman for the PYD in Germany.
However, claims in a statement accompanying the ceasefire that the PYD and Arab anti-regime fighters would work together against the Al Assad regime were greeted with scepticism.
"They deeply distrust each other, push broadly divergent agendas, and compete over scarce resources, which is what led to clashes in the first place," said Peter Harling, a Syria analyst with the International Crisis Group.
Wladimir van Wilgenburg, a Middle East analyst with the Washington-based Jamestown Foundation, said the PYD appeared to be maintaining a policy of protecting its areas from outside forces when attacked, but not going on the offensive.
"Their traditional line is that they would not allow any other forces in the Kurdish-dominated areas they control," Mr van Wilgenburg said, noting the reported intention of Arab anti-regime fighters to push farther east into predominantly Kurdish areas.
"Many Islamist armed groups and FSA insurgents are hostile towards Kurdish autonomy and the secular Kurdish parties, and this might result in more clashes."
Tensions have long existed between Arabs and Kurds in the oil-rich Jazira region, which has a mixed population of Arabs, Kurds and Christians.
Kurds dominate the region's north-east, but Arabs believe them to be interlopers who arrived in the area from Turkey early in the 20th century. The Arab-dominated Syrian political opposition currently refuses Kurdish demands for autonomy in a post-Assad Syria and accuses the PYD of collaborating with the regime.