Pakistan has shut off a crucial supply route to Afghanistan used by U.S. and NATO forces. The move is in apparent retaliation for a cross-border raid into Pakistan by Western troops who were stationed in Afghanistan. It's unclear whether the troops were permitted to cross the border, but in either case it has infuriated Pakistani leaders who see their country's sovereignty at risk. Pakistan's shut-down of the heavily trafficked border crossing, one of only two land routes across the Afghanistan-Pakistan border, comes as President Barack Obama struggles to bring about the Pakistani leadership. Here's what this troubling incident means.

• Low Point in Tenuous U.S.-Pakistan Relationship  The New York Times' Ismail Khan and Jane Perlez write, "A closure of the crossing through which NATO and American troops receive most of their non-lethal equipment is rare, and signaled a worsening in the military relationship between Pakistan and the United States just three months before the Obama administration takes stock of progress in Afghanistan. The Pakistani interior minister, Rehman Malik indicated that NATO strikes in Pakistan were being taken extremely seriously. 'We will have to see whether we are allies or enemies,' he said Thursday."

• Why Pakistan Is Furious  Al Jazeera explains, "Over the weekend, Nato helicopters fired on targets in Pakistan at least two times, killing several suspected fighters they allegedly pursued over the border from Afghanistan. Pakistan's government protested against the attacks, which came in a month during which there have been an unprecedented number of drone missile attacks in the country's northwest. Pakistan also threatened to stop providing protection to Nato convoys if the military alliance's helicopters attacked targeted inside Pakistan again."

• Pakistani Blogger: Is Helping the U.S. War Still Worth It?  A blogger writing under the Shyema for the Pakistani newspaper Dawn evaluates, "On one hand we are receiving so much funding and aid and on the other hand, our sovereignty is being ridiculed by daily drone strikes and now the chopper violations. ... With friends like these. ... There may not be a black and white solution to the militancy but the establishment does need to decide, is it happy with the assistance (read: violation of sovereignty) or not?"

• 'America's Pakistan Problem'  Time's Michael Crowley is not optimistic. "There are several reasons to believe [the U.S. struggle for Pakistan] is going even worse than the one bogging down roughly 100,000 American troops in Afghanistan," he writes. "The fate of Pakistan and its nuclear arsenal was central to President Obama's thinking when he deployed 30,000 more troops to Afghanistan last year. Obama believes that chaos and free rein for militants across the border presents an unacceptable threat to the stability of Pakistan. But the U.S. military campaign in Afghanistan is making slow headway, and Obama has vowed to begin withdrawing troops from the country next summer. The chances that America's Pakistan problem will be solved by then appear extremely dim. Which leaves Barack Obama still in search of a winning strategy for his real war."

• Pakistani Newspaper: 'By Helping America, Pakistan Kills Itself'  Pakistani newspaper The Nation published a staff editorial on Tuesday that provides a window into the Pakistani thinking behind the border-blocking. "By Helping American, Pakistan Kills Itself," reads the headline. "As so many have said, if the Pakistani state doesn't delink from America's misguided 'War on Terror', the Americans would eventually shift the center of gravity of its war from Afghanistan and move militarily into Pakistan. But now, that is precisely what's happening. For quite sometime, the U.S. has been carrying out drone attacks and killing thousands of innocent Pakistani citizens - perhaps in the process, killing a few militants as well." A U.S. invasion of Pakistan is a long-held and widespread fear in Pakistan.

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