"We have lost a lot by declaring Russia more or less an enemy," the 53-year-old MiG ace said in a recent radio interview
Bulgarian Prime Minister Boyko Borisov's candidate for president appeared headed for defeat to a left-leaning opposition candidate in the first round of elections, official results confirmed Monday, setting up a tense November 13 runoff.
Tsetska Tsacheva won 22.0 percent of the vote behind Rumen Radev on 25.7 percent, the candidate of the opposition Socialists, the national election commission said on the basis of over two-thirds of votes counted.
The results were broadly in line with exit polls and projections released late Sunday.
A defeat for Tsacheva would be an embarrassing setback for the centre-right Borisov, 57, the burly former police chief who has been premier since late 2014.
Borisov had said before Sunday's first round that he would resign and call fresh elections if Tsacheva, who is speaker of parliament, failed to beat former air force commander Radev in the first round.
But late Sunday Borisov rolled back on this, saying that he would throw in the towel if Tsacheva, 58, fails to be elected Bulgaria's first female head of state next Sunday.
New elections could plunge the EU's poorest and arguably most corrupt country -- the average monthly salary is just 480 euros ($535) -- into renewed political turmoil.
A victory for Radev could also see ex-communist Bulgaria, which has long walked a tightrope between Moscow and Brussels, tilt more towards Russia. He has called for EU sanctions imposed on Russia over Ukraine to be lifted.
"We have lost a lot by declaring Russia more or less an enemy," the 53-year-old MiG ace said in a recent radio interview.
Radev has also said however that "a necessary improvement in relations with Russia doesn't mean a retreat from Euro-Atlantic values."
The job of Bulgarian president is largely ceremonial but he or she is still a respected figure with some powers.