U.S. troops shot at from Pakistan more often

America has been engaged in a shooting war with a country that's supposed to be an ally. A top U.S. general said American troops in Afghanistan are increasingly coming under fire from across the border in Pakistan.

CBS News correspondent David Martin reports that American outposts on the Afghan side of the border have experienced a dramatic increase in mortar and rocket attacks launched from inside Pakistan.

"The cross border fires this year...are over four times higher than they had been in the past years, so considerably higher," said Lt. Gen. Curtis Scaparotti, commander of U.S. forces in Afghanistan.

It's not just the increase that worries Scaparotti, but the fact that some of the attacks are carried out under the noses of the Pakistani military, which does nothing to stop them.

"We have seen indications where fires have originated from positions that were in close proximity to some Pakistan outposts, which, as you might imagine, give us great concern," Scaparotti said.

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The attacks are occurring in an area controlled by the Haqqani network, a violent insurgent faction which U.S. officials say is supported by Pakistani intelligence. It is a baffling double game in which, as Secretary of State Hillary Clinton explained, Pakistan supports Haqqani attacks on Americans, like the one last month on the U.S. embassy in Kabul, while at the same time setting up a secret meeting between the U.S. and the Haqqanis.

"This was done in part because I think the Pakistanis hoped to be able to move the Haqqani network toward some kind of peace negotiation, and the answer was an attack on our embassy," Clinton said.

Last week, Clinton warned the Pakistanis there would be "a very big price" to pay if they continue supporting terrorists.

Since then, a Pentagon official says, there have been no reports of cross border shelling.