No one knows what will happen in Egypt in the next few days -- will the Mubarak government succeed in clamping down on demonstrators and put an end to the reform movement? With his speech on Friday, explaining that he's asked his cabinet to resign, will Mubarak's moves quell the unrest? Will Mubarak manage to stay in power by offering political and economic reforms? Or is he finished? If so, what happens next?

No one knows the answer to those questions, including the Egyptians themselves. But these demonstrations have the potential of being like the fall of the Berlin Wall, with ramifications for every Muslim country from Tunisia to Iran.

What the U.S. must do is what we did when the Berlin Wall fell, make sure that "what happens next” are pro-western governments with strong ties to the U.S. Why? Because if the Mubarak government does fall, the worst of all possible outcomes is if Obama “does a Carter,” and Egypt ends up with a radical Islamist government like Iran.

So far, the Obama administration seems unsure how to respond to the Egyptian demonstrations. They’ve done everything from seeming to support the country's democratic movements to seeming to support Mubarak’s continued efforts to remain in office.

The Obama administration must proceed very carefully because what happens next in Egypt will affect U.S. interests now and for years to come.

From what we can tell, the Egyptians taking to the streets in Cairo appear to be young, well-educated, and pro-democracy. They’re demanding economic and political reforms for a country that has been ruled for 30 years by a dictator who is corrupt and incompetent and has left their country in economic chaos.

They are NOT – at this point – motivated by religion. They do NOT want to replace President Mubarak with an Islamic regime of ayatollahs.

But, as happened with Iran in 1978 when the Shah was toppled, what started as a pro-democracy movement can very quickly be brushed aside by radical Islamists, like the Muslim Brotherhood.

In revolutions, the group that ultimately prevails is often the one that is better organized and more ruthless in eliminating its rivals.

We shouldn’t pull out the rug from the Mubarak government, like President Carter did with the Shah of Iran. But we shouldn’t prop them it up either.

We should be talking, frequently, with both sides. If the Mubarak government does fall, it could be replaced by a pro-democracy government, perhaps headed by Nobel Laureate Mohammed El-Baradei.

That’s when the .U.S must rush to Egypt’s side with aid, support, encouragement. And President Obama, who made an historic speech at Cairo University two years ago urging reform and democracy, is uniquely situated to do so.

Whatever happens next in Egypt, or Tunisia or other countries if the movement spreads, we need to be part of it. Because what often happens in revolutionary situations -- from Russia to Iran -- is that history unfolds as a three act play: The first act topples the dictator, the second act is the reform democratic government and the third act is all about the brutal extremists.

Kathleen Troia "K.T." McFarland is a Fox News National Security Analyst and host of FoxNews.com's DefCon 3. She is a Distinguished Adviser to the Foundation for the Defense of Democracies and served in national security posts in the Nixon, Ford and Reagan administrations. She wrote Secretary of Defense Weinberger’s November 1984 "Principles of War Speech" which laid out the Weinberger Doctrine. Be sure to watch "K.T." every Monday at 10 a.m. ET on FoxNews.com's "DefCon3" already one of the Web's most watched national security programs.