Sen. Jim Webb sent a letter today to the White House warning President Bush not to take offensive military action against Iran without the consent of Congress. The issue has recently cropped up in the presidential race, where Sen. Barack Obama former Sen. John Edwards have criticized Sen. Hillary Clinton for voting in favor of an amendment designating a wing of the Iranian Revolutionary Guard as a terrorist organization.

Obama spent much of Tuesday's debate on the issue, hitting Clinton for offering the president what he characterized as the first steps down the path toward the use of force against Iran. But in what is apparently a missed opportunity to drive the point home, Obama was not among the 29 senators who signed on to Webb's letter. One source familiar with the process said Obama's office was among those asked several times to sign on. Clinton, however, did sign on.

Webb, who has recently become one of the party's leading voices on military issues, was joined by Clinton along with top Democratic Sens. Dick Durbin, John Kerry and Jack Reed, among others, in affirming that congressional authority was not granted by an amendment designating the Quds Force a terrorist organization. That amendment, offered by Sens. Jon Kyl and Joe Lieberman, "should in no way be interpreted as a predicate for the use of military force in Iran," the letter reads.

The missed opportunity is not the first time Obama's Senate record has been put seemingly at odds with his campaign rhetoric on the issue. Obama's argument against Clinton has been questioned by some, who noted he missed the vote on the Kyl-Lieberman amendment in order to campaign.

Neither Obama's Senate office nor his campaign office returned multiple calls and emails seeking comment. UPDATE: Obama's office emailed through the following statement:

Senator Obama admires Senator Webb and his sincere and tireless efforts on this issue. But it will take more than a letter to prevent this administration from using the language contained within the Kyl-Lieberman resolution to justify military action in Iran. This requires a legislative answer and Senator Obama intends to propose one.

Full letter below the jump.