It’s significant because it is not the first time it has happened.  Once might point to a misunderstanding.  But the Pakistan Army has again fired on U.S. troops.

Pakistani and American ground troops exchanged fire along the border with Afghanistan on Thursday after the Pakistanis shot at two American helicopters, ratcheting up tensions as the United States increases its attacks against militants from Al Qaeda and the Taliban, who are being sheltered in Pakistan’s restive tribal areas.

The two American OH-58 Kiowa reconnaissance helicopters were not damaged and no casualties were reported on either side from the ground fire. But American and Pakistani officials agreed on little else about what happened in the fleeting mid-afternoon clash between the allied troops.

American and NATO officials said that the two helicopters were flying about one mile inside Afghan air space to protect an American and Afghan patrol on the ground when the aircraft were fired on by small-caliber arms fire from a Pakistani military checkpoint near Tanai district in Khost Province.

In response, the American ground troops shot short bursts of warning fire, which hit well shy of the rocky, hilltop checkpoint, and the Pakistanis fired back, said Rear Adm. Gregory Smith, a spokesman for the Central Command.

But a spokesman for the Pakistani army, Maj. Gen. Athar Abbas, said Pakistani forces fired warning shots at the American aircraft after they crossed into Pakistan’s territory in the area of Saidgai, in North Waziristan’s Ghulam Khan region. “On this, the helicopters returned fire and flew back,” General Abbas said.

Local residents said that one of the two helicopters had entered inside Pakistan territory by about a mile, while the other hovered on the Afghan side of the border.

“When our forces fired warning shots, we were a little scared of a possible retaliatory fire from the helicopters,” said one of the residents, Haji Said Rehman Gorbaz. “But we were happy to see the helicopter flying back into Afghanistan. We were happy that our forces fired at the helicopter.”

There was disagreement between nations, but the Pakistani position concerning U.S. troops seems certain.

“Just as we will not let Pakistan’s territory be used by terrorists for attacks against our people and our neighbors, we cannot allow our territory and our sovereignty to be violated by our friends,” Pakistani President Asif Ali Zardari said in New York on Thursday.

But in Washington, Pentagon spokesman Bryan Whitman insisted the helicopters had not entered Pakistan. He described the incident as “troubling” and called on Islamabad for an explanation.

“The flight path of the helicopters at no point took them over Pakistan,” he said. “The Pakistanis have to provide us with a better understanding of why this took place.”

Pakistan later amended their position.  “Pakistan’s new president said Thursday his military fired only “flares” at foreign helicopters that he claimed had strayed across the border from Afghanistan into his country.  Pakistani President Asif Ali Zardari said his forces fired only as a way “to make sure that they know that they crossed the border line.”

It makes no difference.  We believe that Pakistan lost its claim to sovereignty over the tribal regions when it ceded its authority and failed to enforce writ in the area.  The time should soon be coming that Pakistan chooses sides in the conflict.  More money cannot continue to pour into the war on the Taliban through Pakistani hands, with Pakistani troops firing on U.S. troops while also failing to enforce writ in the region.

Finally, every minute spent on worrying over U.S. incursions into the tribal areas is a minute wasted, better spent on Pakistan crafting a plan to continue to exist and do so without total surrender to Sharia and Taliban rule.  Pakistan is on a precarious perch, and is in dire trouble concerning its future.  The focus on U.S. troops shows that it does not yet comprehend the trouble at hand.  When the Pakistan Army sees U.S. forces flying overhead, they should wonder where the U.S. is going and why they aren’t participating.  So is Pakistan a friend or enemy of the U.S.?  It is a dangerous thing to be an enemy of the U.S.