Secretary of State John Kerry told House Democrats that Turkey -- along with Saudi Arabia and the United Arab Emirates -- has already offered military assets for any Syrian attacks, two sources on the call told CNN this week.
If so, Turkey could play a huge role: There are already two big U.S. air bases there that could be used by fighter jets, refueling tankers, AWACS surveillance planes and U2 spy aircraft. There are also U.S. defense missile systems on the Turkish border as a defense against Syria.
Tell me more about oil-rich Saudi Arabia
Analysts believe that Saudi Arabia heavily influenced the recent announcement by the Arab League foreign ministers who called upon the international community to punish the Syrian regime for its alleged use of chemical weapons.
That statement was interpreted as the Arab League "green-lighting" a military strike against Syria without specifically mentioning bombing.
With its vast air force and bases, Saudi Arabia would offer a lot of resources to Western militaries. But it wouldn't participate directly in any attack on Syria because that would inflame a widespread Arabian Peninsula antipathy against Western military forces intruding into Arab affairs.
Still, Saudi Arabia is a diplomatic heavyweight in the Arab world, so the country's tacit support and money would ease any U.S. burden if it is forced to act alone against Syria.
Kerry told the House Foreign Affairs Committee this week that Arab countries -- presumably including Saudi Arabia -- have offered to help bear the financial cost of the proposed military offensive against Syria.
"That's how dedicated they are to this," Kerry said.
U.S. ally Jordan is in a bind
Like Saudi Arabia, Jordan has air bases close to Syria's border that could be useful for inserting and extracting special forces and mounting rescue missions for downed pilots. Jordan also hosts U.S. forces, and together they train rebels for combat in Syria.
The Jordanians also allow weapons to flow over its border to the Syrian opposition, and their country is home to one of the biggest CIA operations on Syria in the region.
But Jordan is perhaps the most vulnerable of U.S. allies because it's so close to Syria and has declared that it won't be a launching pad for Syrian attacks. Jordan is unlikely to be involved directly in a U.S. strike against Syria because Jordan could face retaliatory missiles and terror attacks from the Syrian regime. Meanwhile, Jordan is nervous about its own internal tensions arising from Arab Spring, including how the country deals with corruption allegations and a not-so-popular king.
"Jordan fears Syria will escalate horizontally and switch the geography of conflict," Martini said.
Could Russia do anything?
Russia has been supportive of the Syrian regime, but if it wanted to assist the United States, it could pull its military advisers out of Syria and stop its alleged supplying of arms to the regime.
Russia could also tell Syrian President Bashar al-Assad to hand over power to an interim administration.
Such Russian support is unlikely, and the most that the Obama administration could expect is Russia expressing uncertainty about whether the Assad regime is the best to govern Syria, as Russia did a year ago.
So what kind of a coalition could we be talking about?
When all is said and done, any U.S.-led coalition against Syria could be one that offers more moral than military support.
That is still important, especially when the nations act outside the aegis of the United Nations Security Council.
"A coalition is political in nature, but the United States would do the heavy lifting militarily," Tabler said.