An insurgent attack killed six foreign soldiers in Afghanistan's Taliban-infested south on Sunday, days before the White House publishes a review of US military strategy in the increasingly deadly war.
Despite record numbers of coalition deaths and talk that the Taliban's reach is spreading, the US assessment is likely to endorse the current strategy amid claims of some battlefield success in the highly volatile south.
But critics say the mounting death toll is indicative of a strengthening insurgency and that it is time to negotiate with the militants to end nine years of violence that is only getting worse.
NATO would not give further details of the latest incident, one of the deadliest single attacks in recent months on foreign soldiers, and would not reveal the nationalities of the dead, in line with policy.
The attack took to 692 the number of foreign soldiers killed so far in 2010, the bloodiest year by far in the conflict, according to an AFP tally based one kept by icasualties.org. In 2009, 521 coalition troops died.
On November 29, six American police training soldiers were killed by one of their Afghan students in eastern Nangarhar province.
The south of the country is the Taliban's heartland, where 15 civilians, including children, were killed Saturday in a roadside bomb blast -- the insurgents' cheaply made weapon of choice that claims most lives in the war.
The rebels were ousted from government in 2001 by a US-led invasion and have since focused their violent bid for a return to power in the south and east of the war-torn country, which both border Pakistan.
The long-awaited US war review, expected to be released at the end of the week, comes a year after President Barack Obama deployed 30,000 extra troops to Afghanistan to combat the growing insurgency.
NATO leaders at a summit last month in Lisbon endorsed plans for the beginning of a "transition" to Afghan forces providing security across the country in 2011, with an aim of ending the combat mission by the end of 2014.
US Defense Secretary Robert Gates on Wednesday said during a visit to Afghanistan that he was "convinced" the US "surge" strategy was paying off.
"The bottom line is that in the last 12 months, we've come a long way, making progress that even just in the last few months has exceeded my expectations," he told reporters in Kabul.
NATO has said it would battle hard through the bitter Afghan winter, which usually signals a lull in fighting.
But the US-led war is facing dwindling support at home as casualties mount.
The coalition's upbeat assessment conflicts with that of a group of influential international experts on Afghanistan, who on Saturday appealed to Obama to radically change his strategy and negotiate directly with the Taliban.
An open letter from 23 researchers, journalists and NGO chiefs said the current strategy was failing as the militants were growing in strength, and a coalition government including the Taliban should be the long-term goal.
"It is better to negotiate now rather than later, since the Taliban will likely be stronger next year.
"The situation on the ground is much worse than a year ago because the Taliban insurgency has made progress across the country," the letter said.
The experts said that offensives in Kandahar and Helmand provinces in the south were "losing the battle for hearts and minds in the Pashtun countryside, with a direct effect on the sustainability of the war."
Afghan President Hamid Karzai has made overtures to the Taliban and other insurgents to negotiate an end to the war, but they have so far said they will not talk until all foreign forces leave the country.