Bulgaria's works to expand its energy infrastructure as part of a planned new route to carry gas between Greece and Ukraine are making progress and are running on schedule, Prime Minister Rumen Radev said on Thursday.

Seeking to counter the influence of Russian oil and gas in southern Europe, the United States last year signed a long-term deal to export liquefied natural gas to Greece, and on through Bulgaria and Romania to Ukraine via the so-called Vertical Gas Corridor, a route that would also allow gas flows in the opposite direction.

"Bulgaria is fulfilling its commitments," Radev said in a joint statement with Greek Prime Minister Kyriakos Mitsotakis in Sofia.

"The Vertical Corridor is being implemented on schedule; we have completed the works in southern Bulgaria and works are underway in northern Bulgaria," Radev said, adding that as part of the scheme, Bulgaria was also working to increase the capacity of the existing gas pipeline with Greece by 2 Bm3 to 5 Bm3.

Radev expressed Bulgaria's interest in taking a role in the management of the northern Greek port of Kavala, as part of a Greek-Bulgarian rail freight corridor scheme to link northern Greece's ports to Bulgaria's ports on the Black Sea and Danube, bypassing the Bosporus strait.

Mitsotakis said that matter mainly hinged on the private investors who now manage part of the port but a scheme that could involve Greek investments in Bulgarian infrastructure could make sense.