Of all the strategic challenges the next President of the United States will face, one of the most difficult will be the growing crisis in Pakistan. A Muslim state with a restless population of more than 165 million, it has become a magnet for foreign terrorists, a staging area for attacks on Western troops in Afghanistan, and a potential threat to the rest of the world.

The unwise decisions of the Bush administration have contributed to the crisis, but Pakistan has been a problem country since it was carved out of British imperial India in 1947. Ruled by military leaders either behind the scenes or as outright dictators for most of its turbulent history, Pakistan has reached the point where it is now in danger of becoming a failed state - a failed state with a nuclear arsenal and a growing Islamist insurgency. It may also be the key to the success or failure of the American-led war against the Taliban and al Qaeda in Afghanistan.

The mistakes of the Bush administration are now obvious. In its pursuit of its “War on Terror,” the administration gave unstinting support to General Pervez Musharraf, who had seized power in 1999, and made him America's chief ally in that part of the world. Billions of dollars in American aid went to the Pakistani military, which spent most of it on weapons that had little use in fighting an insurgency. And, like previous American administrations, the Bush administration turned a blind eye to the faults of the Pakistani leadership, and even to its illegal nuclear weapons program and the fact that it was selling its nuclear technology to America's enemies, including Libya, North Korea and Iran.

The United States has received little in return. In fact, elements of the Pakistani armed forces – especially their intelligence service – have actually aided and supported the Taliban, who have found sanctuary in the Pakistani tribal areas along the border with Afghanistan. These badlands have never been fully under the control of the Pakistani central government, and when Musharraf sent troops into them in 2004 under pressure from Washington, he failed to root out the terrorists. Whether that was due to incompetence or lack of really trying, he nevertheless left the terrain to the enemy.

Waziristan and other areas of the border have now fallen under control of the Taliban. They have become a launching pad for attacks on Afghanistan by the Taliban as well as wannabe terrorists from other countries who are flocking to Pakistan like the earlier generation of jihadis who went to Afghanistan to fight the Russians. A new wing of the Taliban is also spreading from the tribal areas to the cities of Pakistan, and poses a potential threat to the stability of the country.

The response of Pakistan's new and nominally civilian government has been incoherent and ineffective, and as the military situation in Afghanistan deteriorates, the Bush administration appears to be preparing to act unilaterally. There are almost daily American air strikes on targets within the tribal areas of Pakistan, and there are reports of a build-up of American and other NATO troops on the Afghan side of the border. Admiral Michael Mullen, chairman of the US Joint Chiefs of Staff, flew to Pakistan last week to confront military officials with evidence of their intelligence service's involvement in attacks on Afghanistan.

General David Petraeus, who has been running the war in Iraq with some success, has been promoted to head of the US Central Command and can be expected to develop a new strategy for Afghanistan as well. It will take time to “surge” additional American troops into Afghanistan – perhaps not until next Spring - but the possibility of the United States staging large cross border raids into Pakistani territory to deny the Taliban and their al Qaeda allies sanctuary now looms on the horizon.

Any such move would be a major escalation and would stir up a hornets' nest of anti-American sentiment in Pakistan, and probably destabilize the already weak central government.

The next American president – whether it is McCain or Obama – will not have much time to make up his mind how to handle Pakistan. He will need both good judgement and sound advice. It is one thing to talk tough on the campaign trail. It's something else to order American troops to invade another country at a time when they already have their hands full with two wars.