Pakistan is halfway around the world from America, but the United States watches what goes on there as if it were a neighbor.

The reason is that Pakistan is one of the world’s most important nations when it comes to U.S. efforts to fight terrorism and wage war in Afghanistan.

Leaders of the terrorist organization al-Qaeda are believed to be hiding in the mountains of northern Pakistan since attacking the United States on September 11, 2001. That region also is believed to have secret camps of the Taliban group, which the U.S. removed from power in Afghanistan for allowing al-Qaeda to train there.

This month, efforts to track down al-Qaeda and the Taliban became more difficult for the United States when the president of Pakistan resigned.

Pakistani President Pervez Musharraf had been an early supporter of U.S. efforts to find al-Qaeda and Taliban leaders in the mountains of his country, which shares a border with Afghanistan.

Some U.S. leaders now question whether he was fully committed to tracking these groups, but his departure makes the job more difficult.

Musharraf was a military leader who had great control over his nation. The government that replaces him will likely include leaders from different parties who may have trouble agreeing or getting along.

And the new leaders may prove even less committed to helping the United States find al-Qaeda or Taliban leaders than Musharraf was.

That worries the State Department, the U.S. government agency that deals with issues in other countries.

As one State Department leader told The Washington Post newspaper, the old “Pakistan is gone, and … you are not going to go back to that Pakistan.”

Located in southern Asia, Pakistan occupies a key position among political hotspots in the world today.

To the north it borders Afghanistan, where the U.S. forces have been engaged in a war against terrorism since 2001.

To the west it borders Iran, whose power and influence are growing in the Middle East as the Iraq war continues.

To the east it borders China — an emerging world superpower — and India, with which it has had a long history of religious tensions and violence.

Now it has no president and an uncertain future.

Pakistan is a Muslim nation, whose official name is the Islamic Republic of Pakistan. It was founded in 1947, when Great Britain divided its territory in the region into a Muslim state — Pakistan — and a Hindu state — India.

Two nations were created because a power sharing agreement could not be reached by the region’s Muslims and Hindus.

Because Pakistan is a Muslim state, radical Islamists have sought refuge there to train and plan actions against the United States and other western countries.

Osama bin Laden, the mastermind of the September 11 attacks, is believed to have hidden in Pakistan’s mountains at least part of the time in the last seven years.