Antonio Guterres praised Ankara for hosting millions of Syrian refugees and asked other countries to share the burden.
United Nations Secretary-General Antonio Guterres met Turkey's Prime Minister Binali Yildirim on Friday and lauded Turkey and its people for letting in refugees.
Guterres was in Istanbul on Friday as part of his first Middle East tour since assuming the role of UN's top diplomat last month.
At a joint press conference with the Turkish prime minister, the UN chief praised the "enormous generosity of the Turkish government and the Turkish people for opening their borders and hearts to their brothers and sisters from Syria and many other parts of the world."
He said Turkey became the largest refugee-hosting country in the world when he served as the UN High Commissioner for Refugees (UNHCR).
"This generosity should be matched," Guterres said, launching an international appeal for "burden sharing."
TRT World 's Ali Mustafa brings more from Istanbul.
The UN chief also said he was "determined" to do his best to facilitate a deal to reunify the divided Mediterranean island of Cyprus.
"I am not optimistic. I am not pessimistic. I am just determined," Guterre's said referring to a popular quote attributed to French economist Jean Monnet, a pioneer of the European Union.
Commenting on the issue of Syria, the UN secretary general dubbed the Turkey-Russia sponsored Astana talks as "essential" in maintaining the ceasefire in the war-torn country and moving the peace process forward.
Guterres is scheduled to meet on Saturday with Turkish President Recep Tayyip Erdogan before travelling to Saudi Arabia.
He took the role of UN chief on January 1 after he was sworn in, in December.