NATO supplies in Pakistan hit again

The attacks have further raised tensions already elevated by Pakistan’s decision to close the Torkham crossing in the northwest in apparent reaction to alleged NATO helicopter strikes on its territory. One of those NATO strikes killed three Pakistani paramilitary soldiers.

The tankers hit today were believed headed for a smaller border crossing at Chaman that remains open.

It was unclear who was behind the attack, but the Pakistani Taliban have claimed responsibility for similar assaults on NATO supplies, including one before dawn Monday that killed four people. The militants said it was revenge for the NATO helicopter incursions.

Counting today’s attack, there have been at least six on the supply convoys since the Torkham closure.

The events of the past week have exposed the often-strained nature of the alliance between Pakistan and the United States. But analysts doubt it will reach a breaking point, because each side is so reliant on the other.

In addition to safe passage for NATO supplies, the United States needs Pakistan to help target Taliban and Al Qaeda militants who stage cross-border attacks against foreign troops in Afghanistan. In return, Pakistan receives billions of dollars in military and civilian assistance that help keep its economy afloat.

Both American and Pakistani officials have predicted the Torkham border crossing will reopen within a few days.

NATO Secretary General Anders Fogh Rasmussen tried to reduce the tension between the two sides Monday by apologizing for last week’s helicopter attack that killed Pakistani troops, saying that the casualties were “unintended’’ and that a joint investigation was underway.