Obama dismisses Howard's Iraq criticism
Democrats have reacted with disdain, with Mr Obama saying if Mr Howard is so strongly supportive of the war in Iraq then he should send another 20,000 Australian troops into battle.
"I would also note that we have close to 140,000 troops in Iraq, and my understanding is Mr Howard has deployed 1,400, so if he is ... to fight the good fight in Iraq, I would suggest that he calls up another 20,000 Australians and sends them to Iraq," Mr Obama told reporters in the mid-western US state of Iowa.
If Mr Howard did not take up the invitation, Mr Obama said the comments became nothing more than "empty rhetoric".
"I think it's flattering that one of George Bush's allies on the other side of the world started attacking me the day after I announced (I would run for the 2008 Democrat presidential nomination)."
Mr Howard started the fight when he criticised Mr Obama's plan to withdraw US combat troops by March 2008.
"If America pulls out of Iraq in March 2008 it can only be in circumstances of defeat," Mr Howard told Nine Network on Sunday.
And if there is one thing a Democrat understands, it's empty rhetoric.