Agreement resulted from mediation efforts by Egypt and Iran to satisfy Turkish demands that Syria end support for PKK.

Turkey and Syria signed an agreement in the Turkish city of Adana in 1998 that defused tension that brought the two nations to the brink of war.

The Syrian-Turkish relationship had been tense since the end of World War I and the demarcation of borders between Syria, previously part of the Ottoman empire, and the Republic of Turkey, its heir.

In the 1990s, the relationship reached a boiling point when the Turkish government decided to build an enormous dam system on the Euphrates and Tigris rivers – which start in eastern Turkey, run through Syria, and end in Iraq – threatening water flow into Syria and endangering its agricultural regions.

In response, the Syrian government increased support for a Syria-based Kurdish separatist Marxist group, the Kurdistan Workers Party (PKK), which conducted attacks on targets inside Turkey.

The Adana agreement was a result of mediation efforts by Egypt and Iran and satisfied Turkish demands that Syria end its support for the PKK, declare the group a “terrorist” organisation, and expel its leader Abdullah Ocalan from the country.

After leaving Syria, Ocalan was in 1999 captured by Turkish intelligence. He was sentenced to life in prison and remains imprisoned in a Turkish jail.

The Adana agreement also stipulated that Turkey and Syria enter a reciprocal deal in which both refrain from engaging in military activity that would jeopardise each other’s security.

Though the agreement is still technically in force, since the Syrian war began in 2011 Turkey has sought the removal of President Bashar al-Assad, severely fraying diplomatic ties.

Russia – a staunch ally of al-Assad – suggested on Tuesday during a meeting between presidents Vladimir Putin and Recep Tayyip Erdogan that any Syrian-Turkish rapprochement should be based on the Adana agreement.

But the proposition has serious hurdles ahead, according to Syrian analysts.

Turkish Foreign Minister Mevlut Cavusoglu, meanwhile, said on Wednesday the al-Assad government “has no capacity” to implement the Adana deal.

Under the Adana agreement, Turkey has the right to chase PKK fighters up to 5km (3 miles) inside the border with Syria – but they cannot remain for long.

On Tuesday, Erdogan and Putin agreed to establish a “safe zone” in northeast Syria and PKK-linked Syrian Kurdish fighters – known as the People’s Protection Units (YPG) – will be forced to withdraw from a vast area of territory.

“If Syria and Turkey implement the Adana formula to the current situation, it will not be in the interest of Turkey as it limits its [military] presence and forces it to recognise the Assad regime,” said Syrian scholar Jamal Barout, head of research and policy studies at the Arab Center for Research and Policy Studies in Qatar.

Barout said if both countries agreed to follow the Adana deal without any changes, it would also complicate the Syrian goverment’s ties with the Kurdish fighters, as both are now allied in response to Turkey’s miltary campaign in northern Syria.

“Not using the Adana formula, the current Turkish operation deep inside Syrian territories will have no meaning other than an aggression against the territories of a sovereign state,” Moscow-based Syria analyst Mahmoud al-Hamza said.

He added that Ankara could use the Adana deal to provide legal justification for Turkish operations inside Syria, because under the 1998 agreement Syria is obligated to prevent Kurdish fighters from using its territory as a staging ground for attacks inside Turkey.

“Turkey will realise its objective of removing [Kurdish armed groups] … away from the borders and so they no longer threaten its national security,” he told Al Jazeera.

Analysts said to facilitate continued Turkish operations, Ankara must also recognise the legitimacy of al-Assad’s rule over Syria.

Al-Hamza argued Russia would want the al-Assad government to have the chance to re-emerge as the only legitimate power and reunify the war-torn country.

“The biggest loser in all of this, in addition to the Syrian people, is [Kurdish armed groups] who have ran out of their usefulness to all competing interests in Syria,” al-Hamza said.

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