Akhir 18, 1432 H/March 23, 2011, SPA -- The construction of the South Stream gas pipeline will begin in 2013 and will be completed by December 2015, dpa quoted an official from the Russian energy giant Gazprom as saying Wednesday in Serbian capital Belgrade. The work will begin simultaneously on segments in all the countries through which the 3,600-kilometre pipeline will run, Gazprom project manager Leonid Chugunov said on the margins of a visit by Russian Prime Minister Vladimir Putin. Putin met with Serbian officials a day after visiting Slovenia, another former Yugoslav republic. He was in the region to offer assurances that the pipeline would go ahead as planned. South Stream aims to circumvent Ukraine, with which Moscow has had several rows over transport costs, to supply Russian gas to Italy and Austria via the Black Sea. A final route has not yet been agreed, but it is expected to pass through Bulgaria, Romania, Serbia, Hungary and Slovenia. Chugunov said, "all necessary documentation to begin work will be ready by 2012." South Stream Moscow represents a challenge to the European Union's Nabucco pipeline project, which seeks to bypass Russia by providing gas to Western Europe from Caspian fields. During Putin's visit to Slovenia on Tuesday, Russian and Slovenian officials signed an agreement setting up a joint venture to build and manage the Slovenian portion of the pipeline.