Some unthinkable possibilities

Quick! Name the country we turn into a parking lot the next time al-Qaida's network pulls off a 9/11. If your knee jerks toward Pakistan instead of Iran, your instincts are sound because conditions are falling into place for that scary scenario to unfold.

No, we won't be toppling a regime - much less nation building - anytime soon in a country of 170 million Muslims (eight times the size of Iraq). But the United States could readily find itself unleashing the "gravest possible consequences" (remember that spooky Cold War phrase?) inside Pakistan's borders - specifically the federally administered tribal areas that border Afghanistan.

This swath of remote mountain ranges has never been effectively governed by distant Islamabad, but it's where the Taliban have - according to The New York Times - recently set up a virtual mini-state. The tribal areas are also where most terrorism experts believe Osama bin Laden and al-Qaida's senior leaders operate openly in secure sanctuary.

This mini-state grew out of a series of peace deals that Pakistan's government felt it had no choice but to offer to thousands of Taliban fighters who've taken up permanent residence in the tribal areas since fleeing Afghanistan. The accords offered the warriors respite from the Pakistani military in exchange for a cessation of cross-border attacks into Afghanistan.

But the net result has been even more frequent incursions, plus the Taliban have used brutal terrorist tactics to subdue any opposition from the indigenous tribes, executing dozens of local leaders who dared stand up to them.

Worse, as the Taliban's grip grows stronger, the mini-state becomes a regional magnet for jihadists eager to get a crack at the 40,000 American and NATO troops operating next door. That means Afghanistan gets far bloodier in 2007, just as Iraq's civil war hits its stride.

Here's the scary scenario: We pull back our troops from combat in Iraq, which means we let the sectarian violence run to its logical conclusion. The downside? Lots of ethnic cleansing forces a de facto partitioning of that fake state. The upside? Iraq stops serving as the central front in the long war on radical extremism because: (a) foreign fighters are driven out by the locals and (b) American military personnel are increasingly off-shored on naval vessels.

Then imagine rising domestic pressure here for a similar pullback in Afghanistan. At that point, we've granted the global jihadist movement the same truce that Pakistan offered the Taliban. Naturally, the Taliban would interpret that standoff as a sign of weakness and eventually its embedded ally, al-Qaida, resumes plotting offensive actions against the American homeland.

This scenario would come close to restoring the pre-9/11 status quo between America and radical Islam, swapping out Iraq for Iran as the Persian Gulf rogue slated for containment.

Now imagine some al-Qaida affiliate lights off a nuclear device inside the United States. While our intelligence agencies can't quite pin down Tehran as the ultimate source (or North Korea, for that matter), we're once again burying thousands of corpses in some major American city. Meanwhile, Osama bin Laden publicly praises Allah from his lair in northwest Pakistan.

Then think about what a sitting U.S. president feels compelled to do next.

Americans, madder than hell, want al-Qaida to know that we're just not going to take it anymore. But they're also convinced that invading large Muslim states get us nothing but thousands more casualties and radicalized regimes.

With John McCain or Rudy Giuliani, the tough-guy approach would be clear: Going nuclear gets you nuclear in return. But don't assume it would be any different for Hillary Clinton as she reaches for Margaret Thatcher's mantle or Barack Obama as he stretches for his own JFK-like mystique.

Sound incredible?

Let me remind you that America's the only government in human history to employ nuclear weapons against an enemy state, and with the Taliban back in the mini-state-sponsoring saddle, a politically correct target now exists.

I neither advocate this possible response nor condemn it. I just think it's essential we know what path we're on in this long war because, under the right conditions, nothing remains unthinkable.