Russian President Vladimir Putin will seek support for an initiative to set up safe zones in Syria backed by peacekeepers when he meets Turkish leader Recep Tayyip Erdogan in the Black Sea resort of Sochi on Wednesday.

Erdogan said in Ankara Tuesday that Syria will be the most important topic at the talks with Putin, which take place a day after the Russian leader discussed the plan for safe zones with U.S. President Donald Trump in what the White House described as a “very good” phone call.

Putin and Trump agreed to step up efforts to cooperate on resolving the Syria conflict and the fight against terrorism, according to U.S. and Russian statements. A senior U.S. diplomat is attending two days of Russian-led talks on Syria that started Tuesday in Kazakhstan and include discussion of the safe areas.

Syria’s opposition is skeptical about the Russian initiative, which calls for the creation of four buffer zones patrolled by forces that could include troops from Russia, Turkey and Iran. The areas would be set up in the northwestern Idlib province, Homs province in the west, the East Ghouta suburb of the capital Damascus and southern Syria.

Opponents of Syrian President Bashar al-Assad want United Nations peacekeepers to be deployed. That’s an idea rejected by the Syrian government, pro-Kremlin newspaper Izvestia reported on Wednesday, citing a ruling party lawmaker in Damascus, Sadji Taama.

Russia has long urged the U.S. to join forces with it in Syria. But Trump’s campaign pledge to cooperate with Putin on defeating Islamic State has run into resistance from Republicans and Democrats who are pushing for a harder line toward Moscow over its meddling in the U.S. election, support for Assad and interference in Ukraine.

Chemical Weapons

The Trump-Putin call was the first between the two leaders since tensions erupted over a U.S. missile strike on Syria last month in response to a chemical weapons attack the U.S. government says was launched by Assad’s forces. The Syrian president and his Russian allies rejected the accusations.

While Assad managed to turn the tide of war in his favor after Russia started an air campaign in September 2015, continued fighting between his forces and rebels backed by the U.S. and its allies including Turkey and Saudi Arabia stand in the way of a political settlement. The conflict has killed an estimated 400,000 people and sent millions more fleeing.

Erdogan said he’ll also discuss the issue of visas with Putin. Russia and Turkey remain at odds over trade restrictions after a chill in relations that lasted for months when the Turkish air force shot down a Russian warplane near the Syrian border in late 2015.

Russia continues to block Turkish tomato imports worth a quarter of a billion dollars a year while Turkey has effectively barred Russian grain and other food supplies that have cost Russian exporters up to $1.5 billion, according to estimates cited by the Kommersant newspaper. Putin and Erdogan may discuss grain supplies to Turkey at the talks, Kremlin spokesman Dmitry Peskov told reporters in Sochi.

The two leaders may also discuss the possible supply of Russia’s advanced S-400 missile-defense system to Turkey, according to Kremlin foreign policy aide Yuri Ushakov.

Putin discussed Syria along with other issues with German Chancellor Angela Merkel in Sochi on Tuesday. Merkel visited Saudi Arabia on Sunday in her capacity as the chair of the Group of 20, which will hold its annual leaders’ summit in Hamburg in July.

Source: bloomberg.com