An Afghan border policeman was killed and two Pakistani soldiers were wounded in an exchange of fire along the border late on Wednesday, May 2 officials from both countries said, a clash likely to unsettle already strained ties between the neighbors, according to Reuters.

A senior Afghan official said hundreds of additional Afghan troops were sent to a disputed border gate after the exchange of fire, which lasted for more than two hours.

The stakes are high. The United States wants Pakistan to help Kabul lure the Taliban to the negotiating table ahead of the withdrawal of NATO combat troops by the end of 2014.

But it doesn't take much to strain relations which have been marred by distrust for decades.

A Pakistani military source said the shooting was sparked by an attack on a Pakistani checkpost. The senior Afghan official said trouble started after Pakistani troops attempted to fortify the border gate. Two Afghan border policemen were wounded.

Afghanistan has grown increasingly frustrated with Pakistan over efforts to pursue an Afghan peace process involving the Taliban, suggesting that Islamabad is intent on keep Afghanistan unstable.