Cameron told NBC TV in the US: "I want Britain to do more. I'll always have to take my parliament with me. We're talking and discussing at the moment, including with the opposition parties in Britain, what more we can do.
"But be in no doubt, we're committed to working with you to destroy the caliphate in both countries," he said.
However, there has been growing expectation that a new vote would clear strikes by the Royal Air Force (RAF) on IS targets in Syria and Iraq.
Cameron's interview to American TV will be seen as further indication of such a vote in UK Parliament soon.
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He is due to use a speech tomorrow to warn young Britons tempted to join IS fighters that they will end up as little more than "cannon fodder".
Cameron is expected to set out the UK government's future strategy to combat radicalisation and extremism.