Turkey on Monday denied it had forged any secret "bargain" with Russia over the future of Syria, despite improving cooperation that led to a deal for evacuations from war-wrecked Aleppo.

Turkey and Russia saw relations plunge to their worst levels since the Cold War last year when a Turkish jet shot down a Russian war plane over Syria.

But a reconciliation deal was signed earlier this year and despite being on opposing sides in the Syria conflict -- with Ankara backing rebels trying to topple Moscow ally President Bashar al-Assad -- the rhetoric has warmed considerably.

This has led to suggestions that Turkey agreed to Russia helping Assad to retake all of Aleppo, while Moscow vowed not to interfere in Turkey's own military operation in northern Syria.

"That's not how we see it," a senior Turkish foreign ministry official said. "It is not like we make a kind of a bargain. We don't see any connection."

In a military operation that began in August, Turkish forces and rebel allies are now pressing on the Syrian town of Al-Bab where they have encountered stiff resistance from jihadists.

"People are more impatient to see more results," said the official. "It is difficult but it will continue."

The comments came as Turkish Foreign Minister Mevlut Cavusoglu, his Russian counterpart Sergei Lavrov, and Foreign Minister Mohammad Javad Zarif of Iran, Assad's other key ally, prepared for unprecedented tripartite talks on the Syria conflict in Moscow on Tuesday.

"The Russians suggested Turkey, Russia and Iran come together for a solution, initially over Aleppo, to be maybe further enlarged to the other parts of Syria," said the Turkish official, expressing hope the talks would provide an "impetus".

"It is not a miracle meeting," said the official. "It will give a good opportunity to understand what is happening."

Meanwhile, the Russian defence ministry announced Defence Minister Sergei Shoigu and his Iranian and Turkish counterparts Hossein Dehghan and Fikri Isik would also be holding an unprecedented meeting in Moscow on the same day.

"The upcoming meeting will be devoted to the discussion of Syrian settlement issues and is aimed at facilitating the implementation of the relevant UN Security Council resolutions," it said.

Despite the flurry in diplomacy, the Turkish official insisted that Ankara was sticking to its position that Assad must go for there to be a solution in Syria.

"No way we can have any contact with the Syrian regime," said the official, denying there had been any secret talks with Assad representatives.

"Someone who is the culprit in the death of 600,000 people cannot be the partner for a solution. With the Russians we agree to disagree on this matter."