The main contenders in this year’s Australian federal elections have been forced into a surprisingly early and forceful debate on the country’s involvement in the US-led coalition in Iraq after an attack by John Howard, the prime minister, on Barack Obama, the US Democratic presidential candidate.

Mr Howard sparked a storm of criticism, and a strong rebuff from Mr Obama, after suggesting on Sunday that terrorists would want Mr Obama elected because of his proposal to withdraw US troops from Iraq by March 2008.