ANKARA (Reuters) - Turkey may hold referendum on constitutional change including a more powerful executive presidency at start of summer next year, Prime Minister Binali Yildirim said on Thursday.

Speaking at a joint press conference with nationalist opposition leader Devlet Bahceli, Yildirim said the ruling AK Party was planning to present to parliament its constitutional change proposal next week. He added that the changes will allow the president to retain ties with his political party.

Erdogan has long sought constitutional change to strengthen what had been in the past a largely ceremonial position. To achieve the majority needed in parliament to trigger a referendum on the issue, the AKP needs the support of nationalist MHP.

(Reporting by Ercan Gurses and Tuvan Gumrukcu; Writing by Ece Toksabay; Editing by Humeyra Pamuk)