President Boris Tadic dismissed parliament and called early elections for May 11 after Prime Minister Vojislav Kostunica refused to govern alongside Tadic's Democratic Party over disagreements on EU integration.
"It is [ratification of the South Stream agreement by parliament] unrealistic, particularly since the energy agreement needs to go through parliament," Oliver Dulic told Belgrade's Tanug news agency.
Russia and Serbia signed an agreement on January 25 as part of the South Stream project to construct a pipeline for the transit of the Russian natural gas through Serbia to the Balkans and on to other European countries.
The pipeline will pump 30 billion cubic meters of Central Asian natural gas to Europe per year. Serbia and Hungary joined the project, already involving Italy and Bulgaria, earlier this year. Greece announced plans to join South Stream last summer.
