After a brief stopover in Kuwait on Saturday, Barack Obama could have been in Baghdad within two hours. Instead, he chose to make Afghanistan the first big destination of his week-long international tour.

The itinerary highlighted the increasing focus on Afghanistan in the US presidential campaign as it becomes clear that, while conditions in Iraq are improving, the original battleground in the "war on terror" has taken a sharp turn for the worse. Mr Obama is expected in Iraq today. But the fact he spent the first two days of a tour designed to bolster his foreign policy credentials in Afghanistan illustrates how the conflict has returned to the centre of the US political debate.

"We have to understand that the situation is precarious and urgent, and I believe this has to be the central focus, the central front, in the battle against terrorism," he told CBS News.

Coalition deaths in Afghanistan have exceeded US fatalities in Iraq for the past two months, culminating in the death of nine soldiers last week in the deadliest insurgent attack for three years.

The deteriorating situation has left Mr Obama and John McCain, his Republican rival, scrambling to refocus attention on a conflict once dubbed the "forgotten war".

Both candidates pledged last week to send two or three additional combat brigades - between 7,000 and 10,000 troops - to Afghanistan if elected.

But while there is growing consensus on the need for reinforcements, the candidates are sharply at odds over what lessons should be drawn from the resurgence by al-Qaeda and the Taliban.

For Mr Obama, it underscores his argument that the US must extricate itself from an unnecessary war in Iraq and refocus on the original battleground in the "war on terror".

For Mr McCain, it highlights the importance of having a resolute and experienced leader in the Oval Office who can turn around Afghanistan just as the "surge" strategy has reduced violence in Iraq .