GENEVA - A U.N. senior official on Thursday voiced optimism that there would be a breakthrough in negotiations to ease exports of Russian fertilisers.

"I am cautiously optimistic that we can have important progress soon," U.N. senior official Rebeca Grynspan told reporters in Geneva. She declined to give further details.

Russian and Ukrainian representatives have previously discussed allowing Russia to resume ammonia exports, used to make fertilisers, in exchange for a prisoner swap that would release a large number of Ukrainian and Russian prisoners.

(Reporting by Emma Farge, editing by Rachel More)