Soldiers based in Northern Ireland are set to teach Ukraine's armed forces how to deal with home-made bombs.
The 2nd Battalion Royal Irish Regiment has already trained 1,000 personnel in infantry, medical and logistical planning.
But that role is being expanded, Defence Secretary Michael Fallon has announced.
The training mission will also share British expertise in urban defensive operations, planning and engineering.
Mr Fallon, who was in Kiev for talks with the country's leadership, said the training would improve the "resilience" of Ukrainian forces who are involved in fighting Russian-backed separatists.