Larger, more sophisticated militant attacks have also caused a sharp rise in Afghan civilian deaths - at least 472 in the first seven months of the year, most in suicide bombings, according to an Associated Press count.

In all, at least 600 Afghan civilians were killed from January through July, a 30 per cent increase from the same period in 2007, according to AP figures compiled from coalition and Afghan officials. That includes at least 128 killed by US or NATO forces.

There are about 33,000 US troops in Afghanistan, the most since the war began, meaning more troops than ever are patrolling this country's mountainous terrain and exposed to ambushes and roadside bombs.

The US military suffered 65 deaths in May, June and July, by far the deadliest three-month period in Afghanistan since the war began in 2001. The previous deadliest three-month period was in the spring of 2005, with 45 US deaths.

In July, more US troops died in Afghanistan than in Iraq for the month, for the first time since the Iraq war started in 2003. In all, 92 US troops have died in Afghanistan in 2008, a pace that would surpass 2007's death toll of 111.

The spike in violence is forcing US leaders, including the Presidential candidates, to call for still more troops.