George W. Bush on Wednesday said the consequences of a US withdrawal from Iraq could echo the “killing fields” genocide that destroyed Cambodia after the US pulled out from Vietnam in the mid-1970s.

In a speech signalling Mr Bush is in no mood to compromise with his Iraq war critics, the US president threw down the gauntlet in advance of Democratic plans next month to revive a congressional vote setting a deadline for withdrawal of most of the 160,000 US troops in Iraq.