Russian President Vladimir Putin has discussed energy cooperation via phone with Serbian President Tomislav Nikolic and Hungarian Prime Minister Viktor Orban.
The Kremlin said Putin discussed "prospects of further interaction in the energy sector" in light of Russia's announcement last week to end the South Stream natural gas pipeline project.
The pipeline would have gone under the Black Sea to Bulgaria and later delivered gas to both Hungary and Serbia.
Belgrade had given strong support for the project, which the European Union said was in violation of some of the EU's antimonopoly laws.
Putin had said that Russia may instead build a pipeline to Turkey and create a gas hub near the Turkish-Greek border to supply gas to Europe.
Orban was criticized by U.S. Senator John McCain (Republican-Arizona) last week for "getting in bed with Vladimir Putin."