* More than 3.5 million Syrians living in Turkey
* Tensions between refugees, Turks have risen
* Erdogan, rival vow to send refugees home after polls
By Daren Butler
ISTANBUL, June 22 (Reuters) - President Tayyip Erdogan and his main rival in Sunday's presidential election have both pledged to send millions of Syrian refugees home, responding to growing unease among voters about the number of migrants in Turkey.
More than 3.5 million Syrian refugees who fled conflict in their country are living in Turkey and their presence has become an election issue, with some Turks viewing them as an economic burden and a threat to jobs.
"Right after the election we aim to make all Syrian lands safe, starting from areas near our border, and to facilitate the return home of all our guests," Erdogan said in a speech in the southeastern city of Gaziantep.
"But to do this we need to get through June 24 (election day) safely. Syria's stability is dependent on Turkey being strong. Otherwise they will break Syria to pieces," he said.
Erdogan has said 200,000 Syrians have already returned to northern Syrian regions now controlled by Turkey and allied Syrian rebel forces after they launched military incursions to drive back Kurdish and Islamic State fighters.
However, securing militarily a large enough region of Syria to allow the return of more than 3 million refugees would be a far greater challenge and would pit Turkey against other powers entrenched in Syria's conflict, including Russia and Iran.
Gaziantep, 50 km (30 miles) from the Syrian border, hosts 383,000 Syrians, nearly 20 percent of its population, according to interior ministry data.
Intercommunal violence between Turks and Syrians tripled in the second half of 2017, with grievances in major cities driving inter-ethnic rivalry, economic inequality and urban violence, a report by the International Crisis Group said in January.
Turks will vote in both presidential and parliamentary elections on Sunday. Opinion polls indicate they may be closer than expected when Erdogan called the votes in April, suggesting he may be pushed to a second-round run-off for the presidency, and his AKP could lose its majority in the 600-seat parliament.
Muharrem Ince, the main opposition CHP's presidential candidate and Erdogan's biggest rival, has repeatedly vowed during his campaign to send Syrians back home.
He repeated the pledge in a rally late on Thursday, saying he would restore ties with Syrian President Bashar al-Assad's government and appoint an ambassador to Damascus within 10 days if elected president.
"With peace policies we will send four million Syrians to Syria with the sound of drums and pipes," he told hundreds of thousands of people in the CHP's western stronghold of Izmir.
It was not clear how Ince's plan to re-establish ties with Damascus would persuade millions of Syrian refugees to return to areas under the control of the Syrian government.
Erdogan has backed rebels fighting to overthrow Assad and says the president should step aside. But he has also been working with Russia and Iran, Assad's allies, on plans they say are aimed at stemming the bloodshed in Syria.
Turkey opened its border to Syrian migrants when conflict began in 2011. Ankara has since reversed its "open door" policy, building a wall along the 911 km (570 mile) frontier.
(Reporting by Daren Butler Editing by Gareth Jones)
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