Rating agency Standard & Poor's (S&P) said on Friday that it could downgrade sovereign debt ratings of oil-exporting countries this year as oil prices continued to decline.

"We had an important number of downgrades last year in Africa, the Middle East and the CIS, and if our outlooks continue to perform as an indicator of where the ratings may next go, more might be coming up this year," S&P's EMEA head of sovereign ratings Moritz Kraemer said in an interview with Reuters.