They are expected to discuss mainly Syria, and exchange views on the upcoming Tehran summit as part of the Astana process.

“Any kind of solidarity with Russia makes someone jealous,” said Erdogan.

Erdogan and Putin have spoken over the phone 16 times this year to discuss regional issues, particularly Syria, and bilateral relations.

The Turkish president has already raised the issue of Idlib with Putin in a telephone conversation in mid-July, saying an attack by the Syrian army there could destroy the Astana peace process.

As part of the Astana format, four de-escalation zones have been established across Syria amid ongoing political efforts to find a peaceful solution to the conflict in the Arab country.

Turkey, Iran and Russia are the guarantors of a countrywide ceasefire in Syria. The three have been mediating a peace process since January 2016 among Syria’s warring sides in Astana, Kazakhstan.

Turkey has set up a series of observation posts in Idlib as part of the deal to reduce fighting between militants and the Syrian government in de-escalation zones.

In recent weeks, Syria's government have recaptured militant strongholds in the southwest.

Syrian soldiers have captured most of the southern province of Dara’a in an offensive that began in June.

In a bid to minimize civilian casualties, both Damascus and Moscow have been initiating talks with militants to make them hand back the areas they control to the government without fighting.

Dara'a was the birthplace of sedition that was born in March 2011 before morphing into a foreign-backed militancy that continues to this day.

Syria’s southwestern region is strategically sensitive because of its proximity to the frontiers with both Jordan and the Israeli-occupied Golan Heights.

The territory’s liberation would cut the much-reported collaboration between Israel and militants and deal a blow to Tel Aviv’s plans to consolidate its grip on the Golan Heights, which has been used by the regime to treat wounded militants over the past few years.