The head of Russia's Security Council was in the Serbian capital, Belgrade, for talks with senior officials.
Nikolai Patrushev, who is believed to be one of Russian President Vladimir Putin's closest associates, on October 26 urged Serbia to sign a "memorandum of understanding" on security relations.
"We have such documents with partners of the utmost trust," he said.
Following talks with Serbian Interior Minister Nebojsa Stefanovic, Patrushev was scheduled to meet with Foreign Minister Ivica Dacic and President Tomislav Nikolic.
Under Nikolic, Serbia has actively pursued membership in the European Union.
However, it has refused to join in sanctions imposed by the EU and others against Russia over its military involvement in Ukraine and its 2014 annexation of the Ukrainian region of Crimea.
