An ad by the National-Iranian council in the Washington Post has a letter to President Obama urging him to resist pressures to attack Iran. The ad is signed by a number of former military and intelligence officials. The ad can be accessed here
Signers of the letter include: ""Retired Army Maj. Gen. Paul Eaton, retired Army Lt. Gen. Robert G. Gard Jr., retired Marine Gen. Joseph Hoar, retired Army Brig. Gen. John H. Johns, retired Army Maj. Gen. Rudolph Ostovich III, former deputy director of National Intelligence for analysis Thomas Fingar, former CIA national intelligence officer Paul Pillar, and retired Army Col. Lawrence Wilkerson.""
The letter claims that war should be undertaken only if the U.S. or an ally is attacked. However Obama is following in the footsteps of Bush with a doctrine of pre-emptive war. Although Obama is certainly more willing than many Republicans to follow a diplomatic route he has assured Netanyahu that a military attack is still on the table. Obama specifically said that he would not settle for containment of a nuclear Iran.
The ad has statements by U.S. officials including Leon Panetta Secretary of Defense and form Defense Secretary Gates that argue attack Iran would be a mistake.
Opposition to attacking Iran is common both among military and intelligence leaders but it seems their point of view is drowned out by hawkish politicians especially among the Republicans and by lobbyists for the Israeli viewpoint. For more see this article.