Ø U.S. may send troops
Ø U.S. may establish no-fly zone over Syria
Ø U.S. may send lethal weapons support to "vetted" rebels
Ø U.S. may support rebels in peace talks
Ø U.S. may do nothing
Ø U.S. may attack Iran
At the same time, Secretary of State John Kerry and others have spoken on the record in favor of the June peace talks that are now scheduled for July. The Russians, as a longtime Syrian government ally, also support peace talks (while joining with China to keep the UN Security Council from acting, although it's not clear what the Security would do, or even if it wants to do anything).
The Russians have also been sending surface to air missiles to the Syrian government, for "defensive" purposes, which the Israelis have found offensive. So far, the Syrians don't seem to have shot down anything flying over Syria.
But those Russian missiles would complicate any plan for a no-fly zone.
Obama White House Sees Arming Syrian Rebels as Some Sort of "Compromise"
The "Syrian rebels," a rubric with apparently no precise meaning, are threatening not to join peace talks unless they get more lethal weapons. At least some are making that threat, and they're the ones we seem to think of most highly. Other rebels, more aligned with Iran or al Qaeda, may well be threatening to attend the peace talks if the American-favored rebels get more weapons and they don't.