KABUL:The commander of U.S. and NATO forces in Afghanistan went on national television Tuesday to apologize for a deadly airstrike, an extraordinary attempt to regain Afghans' trust while a mass offensive continues against the Taliban in the south.

Two U.S. Marine battalions, accompanied by Afghan troops, pushing from the north and south of the insurgent stronghold of Marjah finally linked up after more than a week, creating a direct route across the town that allows convoys to supply ammunition and reinforcements.

In a video translated into the Afghan languages of Dari and Pashto and broadcast on Afghan television, a stern Gen. Stanley McChrystal apologized for the strike in central Uruzgan province that Afghan officials say killed at least 21 people. The video was also posted on a NATO Web site.

"I pledge to strengthen our efforts to regain your trust to build a brighter future for all Afghans," McChrystal said in the video. "I have instituted a thorough investigation to prevent this from happening again."

Sunday's attack by NATO jets on a convoy of cars was the deadliest attack on civilians in six months and prompted a sharp rebuke from the Afghan government. McChrystal apologized directly to President Hamid Karzai shortly after the incident. The video is another sign of the military coalition's intense campaign to win public backing for the Marjah offensive with a strategy that involves taking all precautions possible to protect civilians.

NATO said McChrystal made a similar apology via video this past fall when U.S. pilots bombed two hijacked fuel tankers near the northern town of Kunduz. Afghan leaders estimated that 30 to 40 civilians were killed.

The civilian deaths occurred as 15,000 NATO, U.S. and Afghan soldiers were in their 10th day of fighting insurgents in the town in Helmand province.

Although the airstrike was not related to the Marjah offensive, civilian casualties undermine NATO's goal of turning back the Taliban and restoring the Afghan people's confidence in their own government — one of the main objectives of the southern operation that hopes to rout the Taliban, set up a local government and rush in aid.

In Berlin, Richard Holbrooke, the U.S. special envoy for Afghanistan and Pakistan, said civilian casualties were "great tragedies," but stressed that Gen. McChrystal has done the utmost to avoid civilian deaths, noting especially the new guidelines restricting airstrikes. Holbrooke added that the insurgents have no qualms in using civilians as shields.

Meanwhile, a Tuesday morning explosion in Lashkar Gah, the capital of Helmand, left eight people dead and at least 16 others wounded, according to the Interior Ministry. Police chief Gen. Asadullah Sherzad said explosives in a parked motorbike were detonated by remote control in front of the traffic department.

The alliance said its planes fired on what was thought to be a group of insurgents in Uruzgan province on their way to attack NATO and Afghan forces. Interior Ministry spokesman Zemeri Bashary said the airstrike hit three minibuses of civilians, which were traveling on a major road near Uruzgan's border with Day Kundi province.

In Marjah on Tuesday, U.S. Marines from the 1st and 3rd Battalions, 6th Marines Regiment finally managed to link up after more than a week of hard marches through insurgent fire and mined poppy fields.

"This is a very important step," said Lt. Col. Brian Christmas, commander of the 3rd Battalion, explaining that NATO forces now control a continuous north-to-south route through town that hinders insurgents' ability to move freely.

Sporadic fighting continued Tuesday as strongly entrenched Taliban units appeared to have regrouped in a heavily defended stronghold to the north.

On Monday, Adm. Mike Mullen, the chairman of the U.S. Joint Chiefs of Staff, told reporters at the Pentagon that the efforts against the Taliban were "messy" and "incredibly wasteful," as was war in general. "But that doesn't mean it's not worth the cost."

The incident in Uruzgan "reminds us of just how fragile and how tragic any move we can make, any move we make can ultimately be," he said.

"These are split-second decisions that commanders in combat on the ground have to make," he added.

Mullen said the troops in Marjah are making "steady, if perhaps a bit slower than anticipated, progress." He cited the prevalence of planted bombs and the care taken to avoid civilian casualties for the slow pace.

Karzai has repeatedly called on NATO to do more to protect civilians during stepped-up military operations.

In recent months, NATO has limited airstrikes and tightened rules of engagement on the battlefield to try to protect the Afghan people and win their loyalty from the Taliban.

It was the second time in nine days that NATO has apologized for killing civilians. On Feb. 14, two U.S. rockets slammed into a home outside Marjah, killing 12 people, including six children. According to NATO, at least 16 civilians have been killed so far during the offensive; human rights groups say the figure is at least 19. Though NATO is working hard to reduce civilian casualties, it has acknowledged that completely eliminating them is difficult.

Bashary said investigators had recovered 21 bodies from the Uruzgan airstrike and that two other people were missing.

The Afghan Cabinet reported a higher death toll, saying 27 civilians were killed, including four women and a child, and 12 other people were injured. The ministers urged NATO to "closely coordinate and exercise maximum care before conducting any military operation" to avoid further civilian casualties.

The toll was the highest involving civilians since last September, when U.S. pilots bombed two hijacked fuel tankers in a German-ordered airstrike near the northern town of Kunduz. Up to 142 people are believed to have died or been injured, German officials said. Afghan leaders estimated that 30 to 40 civilians were killed.

The controversy about the Uruzgan strike came as a suicide bomber detonated explosives at a community meeting Monday in eastern Afghanistan, killing 15 civilians including a prominent tribal leader widely criticized for failing to prevent Osama bin Laden's escape at Tora Bora after the Sept. 11, 2001, attacks in the United States.

Haji Zaman was one of the two principal Afghan warlords who went after bin Laden after the Taliban fled Kabul in 2001. The suicide bombing occurred outside Jalalabad, the capital of Nangarhar province.

On Tuesday, a second bombing targeting a police convoy near Jalalabad left two civilians dead and two others injured, the Interior Ministry said. No police were injured in the incident.

NATO reported that one service member died Tuesday after being hit by a roadside bomb but gave no details on nationality. Romania's Defense Ministry reported that a Romanian soldier had been killed and another injured when their convoy was hit by a roadside bomb. Romania has 1,035 troops in Afghanistan as part of NATO forces.