| KANDAHAR, Afghanistan
KANDAHAR, Afghanistan An insurgent attack in south Afghanistan killed at least six foreign troops and two Afghan soldiers on Sunday, officials said, days before Washington is due to complete a review of its war strategy.
General Abdul Hameed, commander of the Afghan army in the south, said a suicide car bomber staged the attack outside a U.S. base in Kandahar province, the heartland of Taliban insurgents.
The NATO-led International Security Assistance Force (ISAF) said six troops were killed in an insurgent attack in southern Afghanistan but declined to give any details or confirm if it was the same incident.
The deaths, underlining the rising tide of violence, come days before President Barack Obama unveils a White House-led review of his Afghanistan war strategy.
A senior administration official said Obama would make a statement on Thursday about the review's findings, which are not expected to lead to major changes in strategy.
The review is expected to conclude that, despite entrenched corruption and weak governance, U.S. and NATO forces are making progress on security in parts of Afghanistan.
Violence is at its worst across the rugged country since the Taliban were ousted in 2001, with military and civilian casualties at record highs.
In a further blow for Obama, his special representative for Pakistan and Afghanistan, veteran diplomat Richard Holbrooke, was in critical condition in Washington after surgery to repair a tear in his aorta.
The attack in the south had the highest toll in a single battlefield incident since a May suicide bomb near a military convoy in Kabul that also killed six.
A border policeman shot dead six U.S. soldiers last month but was on a training exercise with the troops he killed and already inside their security cordon when he opened fire.
Hameed said the bomber in Kandahar tried to enter the U.S. base but his vehicle detonated at a gate outside. It was not clear whether the device went off prematurely or the bomber had been killed by guards, he said.
Beyond those killed, three Afghans and four foreign soldiers were wounded.
Taliban spokesman Qari Mohammad Yousuf claimed responsibility for the attack on behalf of the Islamist group.
"It was one of our suicide bombers, who used a minibus for this attack on the base," he told Reuters by telephone from an undisclosed location.
Intensified fighting killed more than 690 foreign troops in 2010, around one third of the total of 2,260 who have died in more than nine years of conflict. June was the bloodiest month ever for foreign forces in Afghanistan, with 103 deaths.
The rise in troop deaths is a major challenge for Obama and his administration, who are under pressure to find an exit from an increasingly unpopular war.
Holbrooke's illness comes just before the White House is due to roll out its assessment of the revised strategy for the troubled region that Obama unveiled a year ago, which included an extra 30,000 U.S. troops.
Afghan President Hamid Karzai joined Obama and other officials in wishing Holbrooke a speedy recovery, saying on Sunday he was "greatly moved" when he learnt of his condition.
But analysts say Holbrooke's absence is unlikely to be a major strategic setback for Obama, as the envoy is just one player in a big team in Kabul and Washington handling a country that is one of the president's foreign policy priorities.
"I don't think it is an immediate concern for the U.S. government because you have a strong group of senior representatives," said Andrew Exum, a Fellow at the Center for a New American Security.
Obama has pledged to start bringing U.S. troops home from next July and begin handing security responsibility to Afghans.
NATO leaders agreed at a summit in Lisbon last month to end combat operations and give security enforcement to Afghan forces by the end of 2014.
Critics say the 2014 target set by Karzai is too ambitious and point to the shortcomings in Afghanistan's security forces.
(Additional reporting by Jonathon Burch and Sayed Salahuddin in Kabul and Ross Colvin in Washington; Writing by Emma Graham-Harrison; Editing by Paul Tait and John O'Callaghan)