ANKARA (Reuters) - Sidelined on his island prison, the one man who might have helped quell a surge in violence in Turkey's Kurdish southeast appears increasingly powerless as a three-year-old peace process teeters on the brink of collapse.
Abdullah Ocalan, whose Kurdistan Workers Party (PKK) first took up arms against the Turkish state in 1984, had been Ankara's main counterparty in talks launched in 2012 by President Tayyip Erdogan to try to end the insurgency.
But as Turkish war planes bomb PKK camps in northern Iraq and Kurdish militants step up their attacks on Turkish soldiers and police, leaving in ruins a ceasefire called by Ocalan in March 2013, his voice is nowhere to be heard.
Pro-Kurdish opposition politicians who acted as intermediaries in the talks have been prevented by the state from visiting the PKK leader, imprisoned on Imrali island in the Marmara Sea, since before a June parliamentary election.
Senior government officials say pledges made by him during the peace process have gone unfulfilled, notably the withdrawal of PKK fighters to bases in northern Iraq, and that until those are honored, Ocalan has no further role to play.
"Our fight will continue until not one terrorist is left within our country and until concrete is poured over (their weapons)," Erdogan said at a military ceremony on Tuesday.
It was a change of tone from the early days of the peace process, which he promoted with slogans including "stop the blood, we don't want the mothers to cry". Unkept promises and the rising power of the Kurdish political opposition have angered nationalists, and forced him to recalculate.
Violence has spiraled, with at least 26 members of the security forces killed since July 20.
On Monday alone, Kurdish militants fired on a military helicopter, killing one soldier, and attacked an armored police vehicle with roadside explosives, killing four officers. The PKK claimed responsibility for the car bombing of an Istanbul police station on the same day.
"If it gets out of control neither the Turkish state nor the PKK will be able to put it back into the bottle. That's the fear," said Gareth Jenkins, an Istanbul-based author and veteran researcher on Kurdish issues in Turkey.
Erdogan, who braved nationalist anger in launching negotiations with the PKK three years ago, has said the peace process has become impossible, but has so far stopped short of formally declaring it over.
In a statement on Monday, the PKK's political umbrella group meanwhile called for a quick resumption of talks between the state and Ocalan but set the release of political prisoners and a strengthened ceasefire agreement as preconditions.
Ankara looks unlikely to concede.
"Ocalan is an actor in the peace process, but the problem is that for him to step in, the PKK group and the HDP (Turkey's pro-Kurdish opposition) must fulfill their promises," said a senior government official familiar with the peace efforts.
"Ultimately, the group has not done what Ocalan wanted."
The HDP has acted as a facilitator in the peace efforts, holding state-sanctioned meetings with Ocalan and sending delegations to speak with PKK fighters in the Qandil mountains of northern Iraq. Their visits had been the only known way for the militant leader to communicate with the guerrillas.
In late July, Erdogan urged parliament to strip politicians with militant links of their immunity from prosecution, a move seen as targeting the HDP in revenge for the June election, when it won 13 percent of the vote and entered parliament for the first time, depriving the ruling party of its majority.
Its leader Selahattin Demirtas, a charismatic former human rights lawyer who campaigned on a progressive platform that took the party beyond its roots in Kurdish nationalism, urged the PKK on Saturday to "remove its finger from the trigger". Reviving peace efforts hinged on reviving Ocalan's ability to negotiate, he said.
Ocalan's intervention helped quell a previous spasm of violence which left dozens dead last year as Kurds rioted over Turkey's reluctance to help their brethren in Syria defend the border town of Kobani against an Islamic State siege.
While Ocalan remains the recognized leader among core PKK fighters, his years of isolation have eroded his influence over the day to day. Qandil, shorthand for the PKK field leadership, was always more hawkish on the peace process, while youth groups with less regard for Ocalan's authority have risen to prominence and are thought to be behind much of the recent violence.
"The Turkish security services have cut off Ocalan. As a result, he has not been able to have much influence during the recent outbreak of conflict," said Jonathan Friedman, Turkey analyst at Stroz Friedberg, a global risk consultancy.
While neither side has an interest in a return to all-out war, nor do they have much incentive for an immediate truce.
For the PKK, such is the fury among Kurdish youth at the renewed violence that to back down now would be to lose face. Erdogan, meanwhile, has political ambitions on his mind.
Turkey could face another election later this autumn if the AK Party which he founded is unable to form a coalition after losing its majority.
Continued violence could stir up nationalist sentiment in support of the AKP and remind non-Kurdish voters, some of whom backed the HDP, of the violent side of Kurdish nationalism.
"It is clear by now that the HDP ... cannot pursue a policy independent of the PKK," Erdogan's spokesman Ibrahim Kalin wrote in the pro-government Daily Sabah on August 4.
In a Reuters interview, Demirtas last month accused the AKP of dragging Turkey into conflict in revenge for its weaker election performance, a charge the government strongly denies. It says the military campaign against the PKK is a response to a surge in attacks on the security forces.
"Erdogan is taking a huge gamble," said Jenkins, the Istanbul-based author, warning that the PKK could increasingly stage attacks in urban centers outside the largely Kurdish southeast, such as Monday's bombing in Istanbul, or lose control of angry Kurdish youths altogether.
"This resentment could pop up in one hundred or one thousand different places, and that's a lot more dangerous than a return to the PKK's insurgency."
Additional reporting by Daren Butler in Istanbul, Orhan Coskun in Ankara; Editing by Nick Tattersall and Janet McBride