Library image of two RAF Typhoons. (Picture: MoD).
The UK is to develop new defence plans with Romania in order to deter further Russian aggression in eastern Europe.
The Defence Secretary said that the British Army will support a Romanian training exercise, known as Scorpions Fury, later this year.
Gavin Williamson also spoke about an incident last week when RAF Typhoons intercepted a Russian bomber looking to infringe NATO airspace.
Four RAF Typhoons and around 150 service personnel, including pilots and technical staff, are involved in an ongoing mission to police the skies over Romania.
They are currently stationed at Constanța as part of NATO's enchanced Air Policing (eAP) mission with American and Romanian forces.
The Ministry of Defence said UK personnel would have a "mentoring role" as part of the partnership with Romania, including a "classroom-based role".
Mr Williamson's commitments emerged after talks with his Romanian counterpart, Mihai Fifor, in Bucharest.
The Cabinet minister cited Russian aggression in Salisbury and increased activity in Ukraine, Moldova and the Black Sea before noting that discussions focused on bringing Romania and the UK "even closer together".
Speaking at a press conference, Mr Williamson said:
"This summer Royal Air Force Typhoons have returned to police the southern skies, only last week intercepting a Russian bomber that was looking to infringe Nato airspace.
"We both committed to meeting the 2% target and the 20% target to spend on equipment that all NATO nations must and should meet.
"Today I announce the British Army will be supporting the Romanian-led multilateral brigade during Exercise Scorpions Fury later this year.
"I can also announce we'll be developing a memorandum of understanding on future defence co-operation that will see us agree an action plan outlining joint activity in the coming years.
"This will also act as a further deterrence to those who wish to do our nations harm."
The Defence Secretary was speaking after making his first visit to Africa, where he told Forces News his first eight months in office have "incredibly challenging".