U.S. Secretary of State Mike Pompeo held talks with visiting Bulgarian Foreign Minister Ekaterina Zaharieva on bilateral ties and other issues here on Monday.

Pompeo and Zaharieva discussed bilateral relations, Bulgaria's military modernization plans, and energy diversification as a European energy security priority, according to a statement issued by the State Department.

The two sides also exchanged views on Iran's ballistic missile program, sanctions on Russia, and the situation of the Western Balkans.

Zaharieva also said that the United States is heading back to the Balkans. She has discussed with Pompeo the Bulgarian idea of creating a gas hub in the Balkans that can be traded with American liquefied gas.

Zaharieva has raised again the issue of visa-free travel for Bulgarian citizens.

She has asked the Secretary of State whether Bulgaria is to become a party in the social agreement with the United States, which recognizes the right and length of service in both countries.

Bulgaria, a NATO member since 2004, signed a defense cooperation agreement with the United States in 2006.

Moscow has regularly accused NATO of boosting its military presence in Eastern Europe, including Bulgaria.