Of the 38 reported attacks so far this year, 10 happened in Kandahar province, the spiritual and traditional home of the Taliban, and 10 happened in neighboring Helmand province, also a heavily Pashtun area.
Ten others were in or near a Haqqani-influenced swath of territory along the southern approaches to Kabul, including the latest attack on Sept. 29 in which Army Sgt. 1st Class Daniel T. Metcalfe, 29, of Liverpool, N.Y., and a U.S. civilian were killed by Afghan soldiers. They were killed in the same district of Wardak province, southwest of Kabul, where a July 3 attack by a rogue Afghan soldier wounded five American soldiers.
"The truth of it is, the removal of this threat completely would be extremely difficult because of the varying nature of the motivations" of the attackers, said Australian Brig. Gen. Roger Noble, a senior operations officer on the staff of the Kabul-based international coalition.
Noble said that while he knew of no Haqqani ties to the attacks, the killings are a means of dividing the Afghans from their allies that is "right up their alley."
Jeffrey Dressler, an analyst at the Washington-based Institute for the Study of War, who has extensively studied the Haqqani network, said Friday that U.S. suspicions may be well-founded.
"If we accept the notion that a proportion of the 'insider attacks' are due to infiltration, then it is absolutely plausible to assume that the Haqqanis are responsible for a portion of those," Dressler said in an email exchange. "The tactic of 'insider attacks' is certainly a potent one, so I would also suspect that the insurgency is doing all it can to increase the frequency and lethality of the incidents."
The Haqqani network has the backing of elements within the Pakistani security establishment and is regarded as one of Afghanistan's most experienced and sophisticated insurgent organizations.
The network maintains a safe haven in North Waziristan, Pakistan, across Afghanistan's southeastern border. The Pakistani Army has consistently refused to launch a military operation in North Waziristan despite the presence there of al-Qaida senior leaders.
Australian Maj. Gen. Stephen Day, the plans chief for the international coalition's joint command, said in an interview that the Haqqanis are a more troublesome military challenge than the Taliban.
"They represent the most dangerous threat because they are the best trained, best resourced opponent we have." Day said Thursday. He was not speaking about the question of a Haqqani link to insider attacks.
When the number and lethality of insider attacks began to accelerate early this year, U.S. and coalition officials were reluctant to release details, including those cases in which the shooter missed or wounded but did not kill his target. The attacks were dismissed as isolated incidents. That changed over the summer as top U.S., Afghan and NATO officials began speaking about them more and publicly pressing for solutions.
Associated Press writer Deb Riechmann contributed to this report.
Robert Burns can be followed on Twitter at http://www.twitter.com/robertburnsAP