A poll in Turkey shows President Recep Tayyip Erdogan ahead of his opponent in what is expected to be a close presidential runoff election. Analysts say undecided voters are likely to affect the outcome of Sunday's vote.

Erdogan will face Kemal Kilicdaroglu, the head of the largest opposition party and the joint candidate of six opposition parties.

Erdogan led the first round of voting on May 14 with about 49.5 percent of the ballots. He has highlighted his achievements as prime minister and president over the past 20 years. Erdogan is also taking credit for helping broker a Russian-Ukrainian deal to export Ukrainian farm products via the Black Sea.

Kilicdaroglu won about 44.8 percent of the votes in the first round. He has criticized Erdogan's response to a plunge in Turkey's currency and runaway inflation, and accused the president of governing with an iron fist.

A survey conducted by Turkish pollster Konda last weekend showed Erdogan leading with a support rate of 47 percent, against Kilicdaroglu's 42.2 percent. Undecided voters accounted for about eight percent.

Erdogan has been endorsed by a nationalist candidate who finished the initial round in third place with about five percent of the votes. But the right-wing party that supported the candidate has given its backing to Kilicdaroglu.