President George W. Bush on Tuesday night made his most pessimistic and assertive defence of his new policy on the war in Iraq as he warned of a “nightmare scenario” of sectarian violence that could draw the entire region into the conflict.

In his annual State of the Union address, Mr Bush - battling criticism over the rationale for going to war and his strategy - sought support of Congress and the American people for sending an additional 21,500 more troops to Iraq.