The prime minister has criticised military chiefs who have spoken out in public about the UK's role in Libya.
It comes after the RAF's second-in-command said "huge" demands were being placed on equipment and personnel.
Mr Cameron said: "There are moments when I wake up and read the newspapers and think: 'I tell you what, you do the fighting and I'll do the talking'."
Last week, the head of the Royal Navy also questioned whether the operation in Libya could be sustained.
Speaking at a news conference in London, Mr Cameron said: "I'm absolutely confident that we can keep this pressure up, we can maintain this mission for as long as is necessary.
BBC News - PM attacks RAF warning over Libya
I cannot believe a serving prime minister has said this. What fkn planet is this man on, when he believes his own bull over that of the experts who are warning him we are taking on too much?