Pro-Western ministers blocked the bid by the nationalists to launch the ratification process for a key energy deal with Russia, stating that parliament and the government do not have the legal authority to adopt strategic agreements.
Only six out of 22 ministers voted in favor and others refused to discuss the deal until early elections have been held on May 11 and a new government formed.
In March, pro-Western President Boris Tadic dismissed parliament and urged new elections after nationalist Prime Minister Vojislav Kostunica refused to govern alongside Tadic's Democratic Party over disagreements on EU integration.
Russia and Serbia signed an agreement on January 25 as part of the South Stream project to construct a pipeline for the transit of Russian natural gas through Serbia to the Balkans and on to other European countries.
The pipeline is expected to 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.
