President Barack Obama walks through the Colonnade on his way...

President Barack Obama walks through the Colonnade on his way to the Oval Office of the White House on Jan. 28, 2014 in Washington, DC. Credit: Getty Images

President Obama is facing perhaps the most difficult foreign policy challenge of his administration with the confrontation with Russian President Vladimir Putin over Ukraine and disputed territory in the Crimean peninsula.

Obama last week said the United States would "stand with the international community in affirming that there will be costs for any military intervention in Ukraine." "If we use force," Putin responded this week, "we have received a request from a legitimate president." He also warned that Europe and the United States would pay a price of their own in the event of economic sanctions.

How should Obama respond to Putin's aggression in Ukraine? Has the president met his match or is he out of his depth? Ben Boychuk and Joel Mathis, the RedBlueAmerica columnists, weigh in.

BEN BOYCHUK: It should go without saying, but we live in an unsubtle age: Nothing that happens in Ukraine - nothing at all - justifies putting the lives of U.S. soldiers, sailors, airmen or Marines on the line.

Encouraging pro-democracy protesters to oust a corrupt government is one thing. Who wasn't thrilled to see Ukrainians stand up to police and armed forces, and cheered when President (and Vladimir Putin puppet) Viktor Yanukovich fled Kiev for Moscow? Using American military might to ensure Yanukovich stays out would be sheer folly.

With that in mind, what exactly does President Obama mean when he says we "stand with the international community" against Russia and presumably in favor of a free and independent Ukraine? The "international community," after all, isn't what it used to be - if it was ever much. The United Nations is powerless here. The U.N. Security Council could issue a sternly worded rebuke, which permanent member Russia would promptly veto.

The European Union doesn't appear too eager to punish Russia economically. Europe - and Germany in particular - relies heavily on Russian gas for heat and electricity. Even our closest ally, Great Britain, has taken steps to protect the assets of Russian oligarchs who live large in London.

As with Syria, which used poison gas against civilians last year in defiance of U.S. warnings, it looks and sounds as if President Obama has drawn another "red line" that he has neither the will nor the wherewithal to enforce.

The other day, German chancellor Angela Merkel reportedly told Obama that Putin is "in another world." Yes, he is. He's in the real world, where real threats are met with real force, where power politics are a zero-sum game, and where "red lines" are not so easily mocked.

By making empty threats and foolish promises, Obama squanders American power and prestige. That makes war more likely, not less.

But surely "standing with the international community" offers some hope? Only for the ignorant and the naive. "Are you quite sure? It would be a pity to be wrong," Winston Churchill wrote in his masterful history of World War I. "Such a mistake could only be made once - once for all."

JOEL MATHIS: There's not much President Obama can do in the Ukraine.

Oh, you'll hear conservatives suggest that if only the president would demonstrate real toughness, Vladimir Putin might be dissuaded from meddling in the affairs of his neighbor nation - a country that, for most of the last century, was part of his nation.

Weekly Standard editor Bill Kristol, of course, has led the way, suggesting that the president should move toward a "security relationship" with Ukraine. Madness, of course. Vladimir Putin is not a noble man, and one sympathizes with Ukrainians who wish to pull their country out from under Russia's thumb. But the United States spent 50 years of the Cold War avoiding a direct armed confrontation with the Soviet Union, because nobody knew if that showdown might lead to a nuclear exchange - and the end of life on earth.

Russia still has a lot of nukes, though, which makes it a dangerous rival. Even if it both countries relied entirely on conventional forces, there's no way the United States would militarily challenge that country just across the border from its home turf, where Russia would necessarily hold the geographic and logistical advantages. Besides: Do you want to sacrifice your child to the cause of Ukrainian sovereignty? Alternatively, it is suggested the president lead the way in imposing international sanctions against Russia. That ignores that many European nations have deep economic ties to Russia that they'll be reluctant to break.

To urge the president to get tougher in in any meaningful way, then, means ignoring that other nations - including Russia - have their own interests, or will drop those interests if only Mr. Obama shows a little more steel than he has. Nonsense.

In fact, the conflict in the Ukraine has pretty much nothing to do with the United States and everything to do with regional power games in a region where the United States has limited power over affairs. Message to American hawks: It's not about us.

Let's keep it that way.

Ben Boychuk is associate editor of the Manhattan Institute's City Journal. Joel Mathisis associate editor for Philadelphia Magazine.