The RAF use drone aircraft such as the pictured Reaper, which can carry bombs and missiles
More money should be spent on the SAS and drones to combat the threat of Islamic State (IS) extremists, David Cameron has told defence chiefs.
The prime minister has asked them to look at increasing funding for special forces as part of the strategic defence and security review.
They have also been urged to consider new spy aircraft, including drones.
The priorities were set out after last week's Budget pledged to spend 2% of national wealth on defence until 2020.
Mr Cameron wants the defence review, due to conclude by the end of the year, to prioritise resources that will help to protect the UK from evolving threats - not only extremism but also a more aggressive Russia and the risks posed by cyber attacks.
The defence chiefs were briefed in a meeting following the unexpected Budget commitment to meet Nato's target of spending 2% of national income on defence every year up to 2020.
Mr Cameron said: "As prime minister, I will always put the national security of our country first.
"That's why it is right that we spend 2% of our GDP on defence because this investment helps to keep us safe. It has only been possible because of the difficult decisions we have made to ensure a strong and secure economy.
"Now we know how much we will spend, what matters next is how we spend it. I have tasked the defence and security chiefs to look specifically at how we do more to counter the threat posed by Islamist extremism.
"This could include more spy planes, drones and Special Forces. In the last five years, I have seen just how vital these assets are in keeping us safe."
The review will also examine how the Royal Navy can work with partners such as the US to use the new aircraft carrier HMS Queen Elizabeth to deploy drones and special forces against terror groups.
The vessel is due to enter service in 2020 and Mr Cameron will welcome some of the ship's company to Downing Street on Monday.
The prime minister will also visit RAF Waddington, the UK's drone base in Lincolnshire, from where operators fly unmanned aircraft over Iraq and Syria.
The RAF's jets and drones are part of the coalition attacking IS in Iraq, but in Syria the drones are limited to a surveillance role - although ministers have begun setting out the case to extend the bombing campaign to the terror group's strongholds in that country.
Mr Cameron has invited acting Labour leader Harriet Harman to a high-level security meeting on Tuesday about the threat posed by IS.
The government is seeking support from Labour MPs to extend the RAF's air campaign to strikes against IS targets in Syria, as well as Iraq.