Putin to hold Syria peace talks with Turkey's Erdogan and Iran's Rouhani

Vladimir Putin will meet with the presidents of Turkey and Iran on Wednesday for a key summit aimed at re-booting the peace process in Syria, a day after the Russian leader hosted surprise talks with Bashar al-Assad.

Putin's meeting with Turkey's Recep Tayyip Erdogan and Iran's President Hassan Rouhani comes as Ankara, Moscow and Tehran cooperate with increasing intensity on ending the civil war in Syria that has claimed some 330,000 lives and made millions homeless.

On Tuesday the Russian president discussed the issue with his US counterpart Donald Trump, with both speaking of the need for progress toward a peace settlement.

The call followed talks with Assad in the Black Sea resort of Sochi "at which the Syrian leader confirmed his commitment to the political process, (and) conducting constitutional reform and presidential and parliamentary elections," the Kremlin said.

Putin's flurry of diplomacy also included phone talks with Saudi Arabia's King Salman and the leaders of Egypt and Israel.

During the phone call with Trump the Kremlin said Putin informed Trump of "the main results" of his meeting with Assad, and stressed the "need to keep Syria's sovereignty, independence and territorial integrity intact."

A political settlement in Syria should be based on principles to be worked out during an all-inclusive "internal negotiating process".

The White House called for the need to ensure "the stability of a unified Syria," a statement said.

The aim is "to peacefully resolve the Syrian civil war, end the humanitarian crisis, allow displaced Syrians to return home and ensure the stability of a unified Syria free of malign intervention and terrorist safe havens," it added.

But there was no mention of Assad's future.

The Syrian president's fate remains a huge stumbling block, preventing global players from reaching a peace settlement over the six-year war.

The Syrian conflict began when the Baath regime, in power since 1963 and led by Assad, responded with military force to peaceful protests demanding democratic reforms during the Arab Spring wave of uprisings, triggering an armed rebellion fuelled by mass defections from the Syrian army.

The brutal tactics pursued mainly by the regime, which have included the use of chemical weapons, sieges, mass executions and torture against civilians have led to war crimes investigations.

In his talks with the Saudi king, Egyptian President Abdel Fattah al-Sisi and Israeli Prime Minister Binyamin Netanyahu, Putin touted Moscow's recent initiative to bring Assad's regime and its opponents together for a "congress".

Different factions of the Syrian opposition will meet from Wednesday in Riyadh in talks hosted by Saudi Arabia.

The aim of the Saudi-backed High Negotiations Committee is to reach consensus on a strategy for UN-backed talks in Geneva, which will focus on a new constitution for Syria and fresh elections.