The Central Bank has also set up a sovereign rating committee to help devise strategies to reduce the country's sovereign risk perceptions.
The committee called for proposals from 10 investment banks before selecting the three, the Central Bank said.
Sri Lanka is rated 'B' by Standard & Poor's and 'B+' by Fitch Ratings, several notches below 'BBB-', the lowest investment grade rating.
S & P's credit analyst Agost Benard said the resumption of an International Monetary Fund deal in July may result in an upgrade during its next rating review.
Sri Lanka is also expected to float a sovereign bond later this year, which will be rated.