Well, Syria has a mutual defense pact with Iran specifically designed against an Israeli attack. So if this happens (which I think is unlikely), expect a Regional war with the USA involved.
And I have absolutely no idea what Iraq will do.
http://news.yahoo.com/s/nm/20060713/ts_nm/mideast_dc_313;_ylt=AnvmKc3..quaWmH1XsxY39QUvioA;_ylu=X3oDMTBiMW04NW9mBHNlYwMlJVRPUCUl
BEIRUT (Reuters) - Israeli Prime Minister Ehud Olmert ordered more intense strikes on Lebanon on Friday, ratcheting up retaliation against Hizbollah guerrillas following the capture of two Israeli soldiers in a cross-border raid.