[Haskell-cafe] posting UTF8 data with Curl library

Hello! I need to submit data to HTTP server using UTF8 encoding. I found out that libcurl for haskell can work with Data.ByteString - but it seems not able to work with Data.ByteString.UTF8. Can you please advice, how do I convert Data.ByteString.UTF8 into Data.ByteString and visa versa? Thank you in advance! -- Eugene Dzhurinsky