The UK is to respond to a NATO request for assistance by sending 85 extra advisers to support its mission in Afghanistan.
The Defence Secretary Sir Michael Fallon said:
"Keeping Afghanistan from becoming a safe haven for transnational terrorists helps to keep our streets safe too.
"That's why we're stepping up our support to the government of Afghanistan and its defence forces, helping them to expand security and develop their armed forces.
"Our extra personnel will remain in a non-combat role, supporting the 500 UK troops already in the country to mentor the future generation of Afghan officers, develop the Afghan Air Force and advise the security ministries."
NATO has confirmed that the alliance will increase the number of troops in Afghanistan by several thousand.
Secretary General, Jens Stoltenberg made the announcement ahead of a meeting of defence ministers in Brussels.
He said the allies have agreed to send more troops to help train and work alongside the Afghan security forces.
"What we do now is not to conduct combat operations but to help the Afghans fight and to help the Afghans take full responsibility for the security in their own country"
Mr Stoltenberg added that the increase does not mean that the alliance will once again fight the Taliban and extremist groups in Afghanistan.
NATO wound down its combat operations in Afghanistan two years ago.