Serbia plans to invest 150 million euros in the construction of a 128-km oil pipeline with Hungary, energy minister Dubravka Djedovic-Handanovic said.Work has already started on drafting the technical documentation for the pipeline that will provide Serbia with Russian Urals crude via the Druzhba oil pipeline, and help Belgrade diversify its energy sources, Djedovic-Handanovic said in a statement.The planned pipeline will transport some four million tonnes of oil. Its construction should be completed before the start of the international exhibition Belgrade Expo 2027.