RM the Syrian rebels! And, while we're at it, give the Israelis the tools they need - bunker-busters, refueling aircraft - so that if they decide to strike Iran's nuclear facilities, they'll get it right the first time.

Both calls have resonated across Washington in recent days. The demand to level the playing field against the Syrian government - which is getting arms from Russia and Iran - came from Senators John McCain and Lindsey Graham. Talk of increasing the credibility of Israel's threat to flatten Iran's far-flung nuclear facilities has arisen in many quarters, from the Republican presidential candidates to think tanks that have charged that the Obama administration has not yet made "all options are on the table" a credible threat.

So far, the White House isn't biting on arms to the Syrian rebels, and it has been deliberately vague on what kind of technology it has shared with the Israelis. The strategic calculus in the two cases is quite different. A humanitarian intervention in Syria would almost certainly become synonymous with a move to engineer regime change, just as the military action in Libya did. The argument over aiding Israel comes down to managing the very public dispute between Washington and Jerusalem over what is the effective way - bombs, sanctions or covert action - to set back, once again, Iran's chances of getting the ultimate weapon.

In a post-Iraq, post-Afghanistan, post-Libya world, the White House reaction to both calls illuminates the conditions under which the 44th president is willing to use force, or see it used by others. But it also sheds light on that ill-defined concept that the administration refuses to call the Obama Doctrine.

Syria and Iran are hardly unrelated problems. In the minds of many on President Obama's team, nothing would undercut Iran's capability to cause trouble in the region faster than if the mullahs lost Bashar al-Assad, Syria's brutal president, as their only ally in the Arab world. The argument commonly heard inside and outside the White House these days is that if the Assad government cracks, Iran's ability to funnel weapons to Hezbollah and Hamas will be badly damaged - and its influence will wither accordingly. Similarly, if Iran's effort to walk up to the edge of a nuclear weapons capability can be set back with a few well-placed GBU-31 bunker-busters, the country's hopes of challenging Israel and Saudi Arabia to be the region's biggest power will be deferred.

Or so the theory goes.

Usually the appeal of providing arms and technology for someone else to do the fighting is undeniable. It's why Franklin D. Roosevelt invented Lend-Lease to provide planes, tanks and ammunition to the British in 1941 when they were broke, and it's how Ronald Reagan got into trouble in the Iran-contra deal, an effort to arm Nicaraguan rebels by diverting funds from a secret arms deal with the country Washington is now sanctioning and sabotaging. At a moment when polls show the country has had its fill of ground wars and the White House talks of "nation-building at home," there is something tempting about handing off weaponry to the rebels and the Israelis, wishing them good luck and reminding them to drop a line back to the White House if any of it works.

"If it was only that easy," one senior national security official told me last week.

The first question that White House officials say they are asking about the Syrian rebels is the same question they asked about Libya 10 months ago: Who are these guys?

In Libya, Mr. Obama took a pass on arming the rebel fighters, electing to join in a NATO air campaign instead. (As it turned out, the United Arab Emirates provided a large number of small arms to help overthrow Col. Muammar el-Qaddafi.)

In Syria, where the death toll is already above 6,000 by most estimates, there is no equivalent NATO operation; so far, a limited intervention to spur a coup or create a "safe zone" for Syrian civilians near the Turkish border is all still talk. So at first glance, providing arms looks like the next-best option. But the worry is that what started as a protest movement has morphed into what Steven Heydemann, a Syria expert at the United States Institute of Peace, described as "a dangerous and uncoordinated array of armed opposition fighters." While there is an entity called the Free Syrian Army - not to be confused with the civilian Syrian National Council - it is less an army than bands of free-form militias. Some are tribal; some are linked by regional or ethnic bonds; there is no real command structure.

THE lesson of past conflicts is that while providing weaponry may help overthrow an odious government, the weapons are often later used to settle scores. The weapons provided to the mujahedeen in Afghanistan helped drive out the Soviets and made for great cinema in "Charlie Wilson's War." But some of those weapons were turned on United States troops after the 2001 American-led invasion.

The concerns about providing high-tech arms to the Israelis are entirely different. There is no closer American ally, and its military is deservedly regarded as among the most disciplined and tightly commanded on the globe. But President Obama now faces the same decision that President George W. Bush did in 2008, when the Israelis sought the bunker-busting bombs and refueling capability they would need for a truly broad, sustained attack on Iran's far-flung nuclear sites.

Inside the Bush White House the Israeli request incited a huge fight. Vice President Dick Cheney, who by his own account advocated an American strike on a nuclear reactor in Syria (the Israelis did the job when Mr. Bush demurred), urged that the Israelis be given everything they needed. The majority of the Bush national security team, however, concluded that if the Israelis were given the technology, it greatly heightened the chances they would use it - and risk another Middle East war. The Obama team has come to the same conclusion.

"This is all about guiding the Israelis to a choice that is most likely to delay the Iranian project without prompting the blowback of an airstrike," one senior member of Mr. Obama's team said after a delegation led by Thomas E. Donilon, the national security adviser, returned from Israel last weekend. The administration argues, publicly and privately, that a mix of sanctions and covert action will be more effective. Which takes us to the Obama doctrine. When it comes to the use of force, it seems to boil down to this: Mr. Obama is willing to use unilateral force when America's direct national interests are threatened - the bin Laden raid is the most vivid example. But when the threat is more diffuse, more a matter of preserving global order, his record shows that he insists on United Nations resolutions and the participation of many allies.

This explains why the Israelis are straining so hard to make the case that in a few years Iran could have a missile capability that could reach the United States - they want to fit Iran into that first category. And it explains Mr. Obama's hesitance to enter a civil war in Syria, where the daily scenes are horrific but American interests are indirect, at best.

David E. Sanger is the chief Washington correspondent for The New York Times.

http://readersupportednews.org/opinion2/289-134/10179-syria-iran-and-the-obama-doctrine