This was announced by State Department spokesman Morgan Ortagus on her Twitter.

Today @SecPompeo spoke with Bulgarian Prime Minister Borissov. #Bulgaria is an important NATO ally and we reaffirmed our commitment to enhance the long-term US-Bulgaria strategic relationship. https://t.co/GuRp5pPMfTpic.twitter.com/VKKwaScNHo

- Morgan Ortagus (@statedeptspox) October 10, 2019

It is noted that another topic of conversation was the importance of diversification in the energy sector.

It is also reported that Pompeo welcomed Bulgaria’s recent purchase of eight F-16 fighter jets.

On December 15, 2018, US Deputy Secretary of State John Sullivan during a meeting with Bulgarian Foreign Minister Ekaterina Zakharieva announced the need for Sofia to increase energy security