Cemil Bayik, co-founder of the PKK, hopes cooperation with US-led coalition against Isis would result in group being de-listed as a terrorist organization

Iraq must remain a united country in order to defeat the jihadis of the Islamic State, a senior leader of the rebel Kurdistan Workers’ Party (PKK) has insisted.

Cemil Bayik, co-founder of the PKK and field commander of the organisation warned that it would be “very dangerous” if Iraq were partitioned. Unless Iraq’s Shia, Sunni and Kurdish communities worked together to counter the threat of Isis, the “fascist” group would benefit, he told the Guardian in an exclusive interview.

“If it (Iraq) is divided, the war will intensify and the threat of Da’esh (Isis) to smaller communities will become greater,” said Bayik, speaking in the group’s Qandil mountain stronghold in northern Iraq. “But if they stay united against Da’esh, they can sort out their differences at a later stage through dialogue.”

Bayik also made clear that the PKK hoped that its cooperation with the US-led international coalition fighting Isis would lead to it being de-listed as a terrorist organization by western countries.

The PKK took up arms in 1984 with the aim of carving out a separate state for Turkey’s 20 million Kurds, but it has since changed its objective to the devolution of power within national borders and is now seeking peace with Ankara.

The group’s imprisoned leader Abdullah Ocalan – known to Kurds as Apo – called a ceasefire from his Turkish prison last year, ordering PKK guerrillas to withdraw to the Qandil Mountains.

Facebook Twitter Pinterest YPG fighters flash victory signs as they ride on an armoured carrier near Mt Sinjar on Monday. Photograph: Reuters

The fate of the peace process is still uncertain, but the PKK has found a new calling in Iraq after coming to the aid of Kurdish peshmerga fighters and the Yazidi community this summer when Isis militants overpowered them in the north.

Peshmerga and PKK guerrillas are now fighting side by side against Isis along a frontline from Syria to eastern Iraq.

Three freshly dug graves in a cemetery in the Qandil mountains are testimony to the latest casualties of this struggle, which has earned the PKK and its sister group in Syria an unprecedented degree of legitimacy from the international community.

The PKK has reaped benefits since the popular uprising against Bashar al-Assad turned to civil war in 2011. Syrian commanders within the PKK – who honed their skills fighting the Turkish army – returned home to train a new force called People’s Protection Units, known by its Kurdish acronym YPG, the armed wing of the Democratic Union Party (PYD), the main Kurdish party in Syria.

“The international coalition’s dealings with the PKK have been conducted through intermediaries and have remained secret,” Bayik revealed. “Diplomatic and military relations should be improved between the coalition and the Kurds in Syria and Iraq to get better results against Da’esh.”

Bayik said the terrorist label was a “great injustice” and that the PKK’s struggle against the “savagery” of Isis proved it was undeserved: “They listed us as a terrorist organisation but our actions against Da’esh proved the opposite,” he said.

Bayik, who wears a pin on his khaki uniform with Ocalan’s face on it, revealed that his fighters have captured Isis foreign fighters on the battlefield and handed over some of them to their respective countries. Bayik said one was a German national detained in Iraqi Kurdistan.

Relations with the Turkish government are still hostile, with Bayik accusing President Recep Tayyip Erdogan of supporting Isis in Syria to destroy the Kurds’ nascent administration. “Turkey wants to destroy the Kurdish cantons or keep them in perpetual fighting to weaken the Kurds … because if you have viable Kurdish administrations in Iraq and Syria, then the Kurds in Turkey will want their own administration too,” he said.

Kurds in Istanbul wave banners depicting PKK leader Abdullah Öcalan,. Photograph: Burhan Özbilici/AP

Bayik said that just as the Isis leader Abu Bakr al-Baghdadi dreamt of becoming the Caliph of all Muslims, Erdogan harbored fantasies of being the head of a revived Ottoman Empire ruling over the Sunnis of the Middle East.

Earlier this month Erdogan surprised many in Turkey by announcing that compulsory classes in Ottoman Turkish (written in Arabic rather than Roman script) will be introduced into the national curriculum – whereas the Kurdish language has not become part of the national curriculum.

The PKK peace process with Turkey has reached a stalemate because Erdogan is not serious about peace, Bayik charged. The president’s real intention was to buy more time so that his Justice and Development party (AKP) could win more votes in elections, consolidate power and change the constitution. “We as the PKK have taken all the steps to move the peace process forward but they haven’t reciprocated,” he said. If Erdogan were serious about peace, he would have released hundreds of political prisoners who are ill or dying in Turkish jails, he added.

Last month Ocalan issued a letter described by Bayik as “a road map” to advance negotiations. The veteran commander said that the PKK leadership has accepted this and are now waiting for Ankara to respond.

“Whatever could be solved through dialogue is already done,” he said. “Now it is time for negotiations and for that, the imprisonment conditions of Apo [Ocalan] should be changed. Until those change, no negotiation is possible”.