Bulgarian Prime Minister Boyko Borisov has officially congratulated Donald Trump after the US real-estate tycoon won Tuesday's presidential election.

"I value exceptionally highly the level of friendship and strategic partnership between our two states. I sincerely believe that under your administration Bulgaria and the United States will continue to build upon what has been achieved," the government press office quotes him saying in a statement to the US President-elect.

While pointing to the the "excellent" cooperation on defense and on fighting terrorism and organized crime, Borisov has expressed his conviction that much more can be done to expand "the presence of American business in Bulgaria."

He has also voiced his hope that the process of US visa liberalization for Bulgarian nationals will be sped up to "increase opportunities for direct links between the two citizens of the two countries."

Borisov's address comes nearly 24 hours after he noted at a regular ministerial meeting: "We should congratulate ourselves on the new American President." He did not elaborate.