A dispute over contracts and debt prompted Russian gas company Gazprom to disrupt gas supplies to Ukraine. The decision left Europeans in the cold for several weeks because about 80 percent of Russian gas bound for Europe moves through Soviet-era pipelines in Ukraine.
Bulgarian Prime Minister Boyko Borisov said he discussed European transit networks and alternative energy resources during talks with European Commission President Jose Manuel Barroso.
"All European Union member states will be obliged to have at least two sources of gas and electricity by 2014," he was quoted by the Sofia News Agency as saying.
He added that European energy concerns would be allayed once the planned Nabucco gas pipeline gets off the ground in 2015.
Nabucco would run through Turkey to Austria, crossing Romania, Bulgaria and Hungary.
The project is meant to break the Russian grip on the European energy sector, though the project had faced obstacles in securing commitments from gas suppliers. Barroso in January signed a joint declaration on gas delivery for Europe with Azeri President Ilham Aliyev in Baku, however.