The top diplomats of Turkey and Russia were set to meet for the first time since Ankara shot down one of Moscow's warplanes as dozens of foreign ministers gathered in Belgrade on Thursday.
US Secretary of State John Kerry was also in the Serbian capital for the annual ministerial council of the Organisation for Security and Cooperation in Europe (OSCE), which he was due to address early Thursday.
The council was expected to focus on the crisis in Ukraine, along with migration, terrorism and other shared challenges, "as well as ways to rebuild consensus on European security as a common project", an OSCE statement said.
Kerry was scheduled to meet Russian Foreign Minister Sergei Lavrov on Thursday, but it was not clear when Lavrov would talk to his Turkey counterpart Mevlut Cavusoglu during the two-day gathering in Belgrade.
The meeting would mark the two countries' first high-level face-to-face talks since the downing of the Russian plane on November 24 along Turkey's border with Syria, which has badly strained relations between Ankara and Moscow.
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On Wednesday the Russian minister said he was willing to meet Cavusoglu, who was "insisting" on holding talks on the sidelines of the council.
"We will not be evading this contact", Lavrov said. "We will hear what Mr. Cavusoglu has to say. Perhaps there will be something new after what has already been said publicly."
After arriving in Belgrade, the Russian told reporters that it would be "sad not to hear anything new" from the Turkish side.
Russia on Wednesday accused Turkish President Recep Tayyip Erdogan and his family of involvement in illegal oil trading with Islamic State jihadists, ratcheting up the heat in the bilateral dispute.
The Turkish strongman accused Moscow of "slander" and has rejected Russian President Vladimir Putin's demands to apologise over the plane incident, saying that Turkey was acting well within its rights to protect its border.
The ministerial council, the governing body of the OSCE, brings together 40 foreign ministers and other high-level diplomats in Belgrade before Serbia passes the chairmanship to Germany for 2016.