The legal grounds on which the use of Ukraine's gas transport system (GTS) will be regulated, and not its ownership structure, matter to the European Union, Head of the EU Delegation to Ukraine Jan Tombinski has said.

"From the viewpoint of the EU, the legal grounds on which the use of Ukraine's gas transport system will be regulated, and not its ownership structure, is the most important issue," he said at a press briefing in Lviv on Friday.

According to the diplomat, from the viewpoint of safety and diversification it is important "that third operators have access to this system."

"Without it, it's difficult to imagine the possibility of extracting shale gas, which is being searched for today, in particular this also refers to western Ukraine, if the [shale gas] producers are unable to deliver it to the GTS. The bases of the functioning of this system should be regulated according to legal principles and it is more important that the ownership structure," Tombinski said.

Tombinski is on an official visit to Lviv region to attend events to mark the Day of Europe.