It's been called the "Wimp Factor".

Americans, it seems, have been less than impressed lately by their Commander-in-Chief's lack of toughness on foreign policy and security issues.

According to the latest poll by the Pew Research Centre released last month, 54 per cent of Americans felt President Barack Obama had been less that convincing in this arena.

Then, along came the Islamic State (IS) group, and Mr Obama had no choice but to step up to the plate with a new strategy to combat this latest terrorist threat.

If some poll ratings reflect unfavourably on Mr Obama's resolving of these policy issues, others have shown there is a growing desire among the US public for IS to be stopped. The jihadist group's brutality and lightning takeover of large swathes of Iraq and Syria have galvanised many Americans and their elected representatives.

"There was absolutely zero appetite ... a year ago for any initiation of hostilities beyond what was absolutely necessary to protect us in a very direct way. Now you see poll ratings in the 70s, people saying IS must be stopped," was how Nancy Pelosi, House of Representatives Democratic Leader and a leading liberal voice in Congress, summed up the current mood.

Realising this, Mr Obama on Wednesday delivered a speech outlining just how he intends dealing with the IS threat.

America's "endless blessings bestow an enduring burden," the president told the nation in an address laying out a four-point plan for tackling the jihadists.

As expected, the plan includes an expansion of airstrikes that will now extend from Iraq to Syria. It will also involve selectively arming and training Syrian rebels on the ground, utilising intelligence assets and special operations forces and providing humanitarian assistance.

So far, so good, some might say. But critics have been quick to point out that a list is not a strategy and to "eradicate a cancer like IS" will need some very deft political and military manoeuvring on behalf of the Obama administration.

Let me just pick up on a few of the more pressing challenges Washington faces. To begin with, for any strategy to be effective, it will require the US to have the support and assistance of its international partners in an attempt to lessen the military and political burden of the operation.

To that end, US Secretary of State John Kerry has been shuttling across the Middle East meeting Arab and other leaders to try to build a solid coalition against IS. On his itinerary were Saudi Arabia and other oil-rich Gulf states as well as Egypt, Jordan, Iraq, Lebanon and Nato member Turkey.

Yesterday this culminated in 10 Arab states agreeing to rally with the US. On Tuesday, Mr Kerry pointed to a broader coalition of more than 40 countries, but what remains unclear is just how substantial the commitment of any of these countries will be.

This too, before the very sensitive issue of juggling two of these "allies", Saudi Arabia and Iran, who are not exactly on the best of terms. In a nutshell, the US faces working with Iranian proxies in Iraq and pro-Saudi actors in Syria.

Fearful at the prospect of Sunni-led IS militants gaining a permanent foothold inside Iraq, the Shi'ite government in Tehran has been providing weapons, intelligence, and military advisers to Baghdad and bolstering the myriad Shi'ite militias fighting alongside the beleaguered Iraqi military.

Washington then will have to work with the Iranians to thwart IS ambitions there.

By contrast, when it comes to Syria, the Americans will have to court Saudi Arabia to influence other Syrian-based Sunni rebel groups to take the war to IS. By far this is where Mr Obama's strategy faces its toughest test.

Just as the US is making gradual progress in supporting an effective fighting force in Iraq in the shape of the Kurdish peshmerga, Sunni tribal forces and Iraqi army soldiers, so it looks to do the same in Syria.

But attacking IS targets there by air while selectively arming and training Syrian rebels on the ground is fraught with logistical and territorial difficulties.

The simple fact is that no matter how much the CIA and US special forces cherry-pick who they train and arm in Syria, it remains other Islamist fighters who control swathes of battlefield territory and are already best disposed to taking on their IS rivals.

Then there is the question of those more moderate Syrian rebel groups concentrated around cities like Aleppo. Can Washington really expect them to turn their guns on IS rather than their sworn enemy, the regime of Bashar al Assad?

Let's not forget too that Mr Assad's beleaguered Alawite - an offshoot of Shia Islam - government in Syria has in great part managed to survive through Iranian military support. Thousands of fighters from Lebanon's Hezbollah - a powerful Shi'ite militia that is armed, trained, and equipped by Iran - have spent the past few years ensuring just this.

Herein lies one of the trickiest things Washington will have to pull off. It needs to back the right Syrian rebels who will take on IS, while at the same time avoiding the creation of a power vacuum that Sunni radicals could fill, jeopardising US efforts to get relations with Iran back on track.

Yes, even by Middle East standards these are complex challenges. The arena Mr Obama is about to step into is no place for wimps.