An American member of the NATO-led force in Afghanistan and a civilian contractor have been killed in a possible insider attack by Afghan security forces, the coalition said Sunday -- putting the war's U.S. death toll over 2,000.

But the International Security Assistance Force later backtracked, saying, according to NPR:

"What was initially reported to have been a suspected Insider Attack is now understood to possibly have involved insurgent fire. The incident occurred while an ISAF unit was manning a temporary check point in an area near an Afghan National Army unit. According to ISAF and ANA reporting, after a short conversation took place between ANA and ISAF personnel firing occurred which resulted in the fatal wounding of an ISAF soldier and the death of his civilian colleague. In an ensuing exchange of fire three ANA personnel are reported to have died."

The Afghan Defense Ministry said the gunbattle was the result of a "misunderstanding" between international forces and Afghan soldiers manning a checkpoint, the Associated Press reported.

The attack came after the United States said joint operations with Afghan forces were returning to normal.

The attack took place in the Sayed Abad district of the Wardak province, according to local police sources, who said a gun battle broke out between coalition soldiers and Afghans when an Afghan National Army member opened fire on American troops.

"Initial reports indicate that a misunderstanding happened between Afghan army soldiers and American soldiers," provincial government spokesman Shahidullah Shahid told the Associated Press. He said investigators had been sent to the site to try to figure out what happened.

In another account, an Afghan official, speaking anonymously because he was not authorized to release details, told the New York Times that a mortar shell had landed amid the American forces, killing a soldier and a civilian contractor and injuring several others. The Americans thought it came from the Afghan National Army checkpoint and attacked it, killing several of the soldiers there, he said.

The provincial police chief Abdul Qayoum Baqizoi said the fight broke out when an Afghan soldier among seven soldiers at the checkpoint opened fire on the Americans; in the ensuing gunbattle, three Afghan soldiers were killed, including the one who had first opened fire.

“We still don’t have a clear picture of what happened,” Baqizoi said. He quoted one of the surviving Afghan soldiers as saying, “I heard some noise and verbal argument and suddenly heard the shooting and then one of the coalition soldiers threw a hand grenade so I fled from the checkpost and hid myself behind our Humvee.”

Joint operations were halted two weeks ago after a surge of attacks on the NATO-led International Security Assistance Force by its Afghan allies. At least 52 ISAF service members have been killed this year in "green-on-blue" attacks.

In an interview that will air on CBS' "60 Minutes" Sunday night, the top U.S. commander in Afghanistan said he is "mad as hell" about the insider attacks.

Gen. John Allen said, "We are willing to sacrifice a lot for this campaign, but we are not willing to be murdered for it," according to a preview by the Voice of America.

Allen said that just as homemade bombs had become the signature weapon of the Iraq war, he believed that in Afghanistan, "the signature attack that we are beginning to see is going to be the insider attack."

A Taliban leader told CBS the insider attacks are part of the militant group's new military strategy.  He said the Taliban has its people planted in the Afghan police and the army.