Breastfeeding Org. -- We LOVE Time Magazine Cover, Except ...

The 3-year-old kid suckling from his mother's teet on the cover of Time Magazine is NOT too old to breastfeed ... so says a powerful breastfeeding organization -- but they do have one gripe.

TMZ spoke with Bettina Forbes -- co-founder of Best for Babes -- an advocacy group dedicated to educating moms about breastfeeding.

Forbes tells us, "We understand that Americans are uncomfortable with [the Time cover], but in cultures where babies wean themselves normally, usually somewhere around age 3 or 4, it is perfectly acceptable."

She adds, "Think of it this way -- some cultures have been drinking green tea for millennia, only recently has it become popular in the United States once the health benefits were understood and it was popularized by marketing ... breastfeeding is the same, it is accepted and valued in many cultures, but not yet fully in the U.S."