"We are deeply concerned about this, from top to bottom," Obama told a White House news conference. But he said the best approach, with the fewest number of deaths in the long run, would be to stick to the plan for shifting security responsibilities to the Afghans.
"We are transitioning to Afghan security, and for us to train them effectively we are in much closer contact our troops are in much closer contact with Afghan troops on an ongoing basis," Obama said. "Part of what we've got to do is to make sure that this model works but it doesn't make our guys more vulnerable."
That vulnerability, however, has been exposed in a strikingly deadly way in recent days.
U.S. officials offer two main theories for why Afghan security forces are turning their weapons on Western partners: infiltration by the Taliban and a U.S.-Afghan culture clash.
Both of those root causes suggest that the problem may get worse as American and other coalition forces shift further into an adviser/mentor role. And that, in turn, raises questions about U.S. ability to train and shape the Afghans into a force that can stand up to the Taliban insurgency after foreign forces end their combat role in 2014.
Jacqueline L. Hazelton, a visiting assistant professor at the University of Rochester, who has extensively studied counterinsurgency strategy, sees the attacks stemming from a combination of Afghan resistance and resentment.
"As disturbing as the attacks are as a Taliban tactic, the broader popular anger revealed - among those the mission is supposed to be most closely allied with and most directly useful to - is even more dangerous for the longer term and reveals a greater rot within," Hazelton said in an email exchange.
Pentagon press secretary George Little said U.S. officials believe the current approach is solid, despite the surge in attacks.
"In the face of this problem, we remain strongly committed to the strategy we have put in place," he said. "The strategy is working, and suggestions that it is fundamentally imperiled at this point are just wrong."
As recently as last week, Defense Secretary Leon Panetta called such attacks "sporadic" and a sign of Taliban desperation. But as the assaults continued through the week, he consulted with his top commander in Kabul and then on Saturday called Afghan President Hamid Karzai to express concern. Obama said Monday he would do the same.
"We've got to make sure we're on top of this," Obama said.
Obama's Republican election rival, Mitt Romney, said Monday in New Hampshire that the U.S. goal ought to be to "transition from our military to their military as soon as possible," in a way that prevents Afghanistan from collapsing and reverting to being a launching pad for terrorist attacks on the U.S.