Britain has not been requested to join strikes against the Islamic State, Downing Street has insisted.
The Times reported that the Pentagon had been exploring whether western allies such as Britain and Australia, and allied Gulf states, would assist in a broader campaign in Syria against the radical group.
The United States has launched scores of bombing attacks on Islamic State (IS) militants in northern Iraq in a bid to assist Kurdish and Iraqi forces in their fightback.
But a No 10 spokeswoman said: "There's been no request for us to deliver air strikes and this is not something under discussion at the moment.
"Our focus remains on supporting the Iraq government and Kurdish forces so that they can counter the threat posed by Isil, for example with the visit of our security envoy to Iraq this week and the provision of supplies to Kurdish forces."
A British family have told ITV News of their devastation after discovering a close relative is fighting with the Islamic State in Iraq.
A French journalist who was held hostage with James Foley in Syria has told ITV News it was "devastating" to see his murder.