Bulgaria's political leaders will insist that Europe continue talks with Russia over the South Stream gas pipeline on the European Council starting in Brussels Thursday.

At the meeting of EU members' Prime Ministers and heads of state, the country intends to maintain that diversification of gas supplies is a key factor for boosting energy security within the bloc, public broadcaster BNR quotes government officials as saying.

A European affairs advisory body with the Council of Ministers earlier refuted statements issued by the EU Commission, which argues subcontractors assigned to carry out the Bulgarian stretch of South Stream were picked in a non-transparent way.

It claimed on Wednesday the gas pipeline's commissioning does not violate European rules and has treated potential subcontractors equally and in a non-discriminatory way.

The advisory panel's stance was approved June 23 as the official one of Bulgaria and is to be reiterated at the European Council. The country had until early July to announce its position on that matter.

Bulgaria has frozen the construction of the pipeline, with Prime Minister Plamen Oresharski explaining he ordered a temporary halt after Brussels launched an infringement procedure against Sofia.

Three things have raised the Commission's concerns, namely the role of South Stream Bulgaria JSC as designer, operator and owner of the pipeline, Bulgaria's capacity to sign a deal on the project with Russia and the tender announced for the construction.

Public procurement was expectedly won by the Russian company Stroytransgaz, where US-sanctioned Gennady Timchenko is the major shareholder.

Serbia, Austria and other countries have however reasserted they are committed to the project.

On Tuesday Austrian energy concern OMV and Russia's Gazprom sealed a deal confirming that South Stream pipes would be built in the country and would deliver 32 billion cubic meters of gas after becoming operational in 2017.