KIEV, Feb. 15 - Yuzhny ammonia prices have risen to record levels so far this year on the back of strong demand from the US, but it remains to be seen how much longer these numbers can be sustained, market sources said on Friday.

Producers are sold out for February, and March business is reported concluded at up to $570/ton FOB (free on board) Yuzhny, up from $380-400/ton FOB at the start of the year.