Britain's PM David Cmeron to pledge extra £12 billion for defence

London: British Prime Minister David Cameron is to promise an additional £12 billion ($18.2 billion, 17.1 billion euros) to strengthen the defence forces when he unveils a five-year strategic review on Monday, according to a government statement.

The Strategic Defence and Security Review will set out Britain's priorities for the duration of his Conservative government, and will focus on tackling threats such as Islamic State group as well as hostile states.

Under the plans there would be nine new maritime surveillance aircraft, and two "Strike Brigades" able to quickly deploy missions up to 5,000 strong, according to a government statement.

"At its heart is an understanding that we cannot choose between conventional defences against state-based threats and the need to counter threats that do not recognise national borders," Cameron wrote of the strategy in a foreword to the review.