FREETOWN (Reuters) - Sierra Leone's ruling party presidential candidate Solomon Berewa said on Monday two main opposition candidates have formed an alliance to try to beat him in an anticipated second round.

Main opposition candidate, Ernest Bai Koroma of the All People's Congress (APC) party, is leading after the first round just over a week ago, with 44 percent of the vote, while Berewa has 38 percent, with around four fifths of votes counted.

The third candidate, Charles Margai of the People's Movement for Democratic Change (PMDC), has 15 percent. If no candidate wins 55 percent, the election will go to a run-off.

"Margai's decision to ally with the APC has not hampered my party's hope to win the presidential election if there is a second round," Berewa, who has said he is disappointed with the results so far, told Reuters.

"It is the democratic right for the PMDC candidate to make his choice as to whatever party he would want his party to ally with," he said in an interview in the capital Freetown.

Officials from both the APC and PMDC declined to comment but said the two parties would be making a joint announcement later.