Diplomat Richard Holbrooke in critical condition

State Department special representative for Afghanistan and Pakistan Richard Holbrooke speaks at the Reuters Washington Summit in New York September 21, 2010.

WASHINGTON (Reuters) - Richard Holbrooke, President Barack Obama's special envoy for Afghanistan and Pakistan, was in critical condition on Saturday after doctors performed surgery to repair a tear in his aorta, the State Department said.

The 69-year-old veteran U.S. diplomat, who brokered the 1995 accord ending the Balkans war, has been a key player in Obama's efforts to turn around the faltering 9-year-old war in Afghanistan, where violence has surged and at least 477 U.S. soldiers have been killed this year alone.

Holbrooke fell ill at the State Department on Friday and was admitted to nearby George Washington University hospital.

"This morning, doctors completed surgery to repair a tear in his aorta," the State Department said in a statement on Saturday. "He is in critical condition and has been joined by his family."

A tear in this major artery of the body -- known as an aortic dissection -- is a painful and life-threatening condition that carries the risk of complications such as stroke, heart attack and kidney failure, according to Dr. Duke Cameron, chief of cardiac surgery at Johns Hopkins Hospital in Baltimore.

Recovery often entails a week in the hospital and another three to four months for full recovery, said Cameron, who is not one of Holbrooke's doctors.

A prolonged absence for Holbrooke could be a blow to Obama's efforts to demonstrate swift progress in Afghanistan next year, when Washington hopes to start putting Afghan forces in the lead and start bringing U.S. troops home in July.

A frequent visitor to both Afghanistan and Pakistan, Holbrooke has personal relationships with the region's leaders while at home he has sought to allay concerns in the U.S. Congress over the course of the war.

Holbrooke's sudden illness comes just before the White House is expected to roll out next week an assessment of the revised strategy for the two troubled countries that Obama unveiled a year ago.

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. The review will not bring any major changes to strategy.

'MOST DIFFICULT JOB'

The aorta carries blood out of the heart to other parts of the body. Upon leaving the heart, the aorta moves up through the chest toward the head then bends and moves down through the chest and abdomen.

"Half of the people who have it (a tear in the aorta) will die within 48 hours if there is no treatment for it," Cameron said in a telephone interview. "Even those who go to surgery, the chance of dying either in the operating room or a short time afterwards in 20 or 25 percent."

With a career that included stints in Vietnam as well as serving as the top U.S. diplomat for East Asia, for Europe and at the United Nations, Holbrooke's most notable achievement has been bringing all sides in the Bosnia conflict to the negotiating table at an air base in Dayton, Ohio. The resulting 1995 Dayton accords ended the conflict.

Holbrooke, who has worked as an executive in the financial sector when not at the State Department, was said to be a candidate for secretary of state before the job went to Hillary Clinton.

During congressional testimony on July 28, Holbrooke conceded that fighting a resurgent Taliban and helping to rebuild Afghanistan were massive tasks. But he repeatedly defended the Obama administration's strategy.

He called the Afghanistan mission "the most difficult job I've had in my career." But, he said, "Number one, on a personal note, I wouldn't be in this job if I thought it was impossible to succeed."

"We're not delusional," Holbrooke added, listing problems in Afghanistan from high illiteracy to trying to help its government be accountable to its own people.

Violence in Afghanistan has soared this year to its highest levels since the Taliban was ousted by U.S.-backed Afghan forces in 2001.

A year ago, when he announced his new strategy, Obama ordered 30,000 more troops to Afghanistan.

Some of those could start coming home in July as foreign troops begin transferring security control to local forces. President Hamid Karzai hopes to have Afghans in the lead across the country by the end of 2014.

(Additional reporting by Glenn Somerville, Arshad Mohammed and Will Dunham; Editing by Vicki Allen and Jackie Frank)