The war in Afghanistan is evolving with a growing number of attacks by Afghan security force personnel on American troops, incidents that have been called "green-on-blue" attacks. It's a term that the Pentagon wants to go away.

So far this year the number of such attacks is nearly double the number for the same period last year. And this year 37 Americans have died, compared with 28 in 2011.

"Make no mistake about it, I've been very concerned about these incidents ... because of the lives lost and because of the potential damage to our partnership efforts," Defense Secretary Leon Panetta said at a Pentagon news conference Tuesday.

Gen. Martin Dempsey, chairman of the Joint Chiefs, said the name "green-on-blue" is a misnomer.

"I think you'll hear us start talking about these incidents more as 'insider attack,' rather than green-on-blue, because what that does is it understates the effect that this is having on the ANSF itself," he said, referring to the Afghan National Security Forces. "You know, they're suffering from the same ... trend that we're suffering from."

Panetta said the attacks, whatever they are called, are a sign the Taliban is getting desperate.

"The reality is, the Taliban has not been able to regain any territory lost, and so they're resorting to these kinds of attacks to create havoc," he said.

There are multiple efforts under way to try to prevent insider attacks, he said.

Gen. John Allen, commander of NATO's International Security Assistance Force, "is meeting with the security ministers to talk about further steps to take in order to protect against these attacks. And he's also meeting with the village elders. These are the people who usually vouch for individuals," Panetta said.

On a separate issue relating to the Afghan conflict, Panetta is upbeat about improving relations with Pakistan.

He said U.S. officials are "encouraged, frankly, that Pakistan has now taken a more positive, visible step to advance our shared objective of a secure and peaceful Afghanistan. Their decision to open up the NATO supply lines means a great deal to us."

Pakistan had shut down the supply lines after a friendly-fire incident last November in which coalition forces killed 24 Pakistani Army soldiers at a checkpoint.

"Similarly, cross-border cooperation with Pakistan is increasing," Panetta said. "General Allen is meeting on a regular basis with (Pakistan's military chief) Gen. (Ashfaq Pervez) Kiyani and trying to improve that kind of cross-border cooperation. And it's helping us try to confront the challenge of these insurgent sanctuaries, which exist on both sides of the border."

Panetta said whether the news from Afghanistan is good or bad, Americans should remember there's a war going on.

"There are a lot of other things going on in this country (the United States) that can draw our attention, from the Olympics to political campaigns to droughts to some of the tragedies we've seen in communities around the country," Panetta said. "But I thought it was important to remind the American people ... that young men and women are dying in order to try to protect this country."