Washington ? The government began building the case toward a possible ban of the popular herb ephedra Friday by proposing strong new warning labels that say the pills can cause heart attacks and strokes or even kill.

The warning labels — first proposed in 1997 but blocked until now by the powerful dietary supplement industry — could be on every bottle by year’s end, the first in a series of Food and Drug Administration steps that could limit, if not stop, the herb’s use.

But the FDA rankled consumer advocates and some members of Congress by stopping short of an immediate ban of the amphetaminelike stimulant used for weight loss and bodybuilding. The FDA said despite reports of at least 100 deaths linked to ephedra use, it had not compiled enough proof of danger to stand up in court under a 1994 law that severely limits federal safety oversight of dietary supplements.

“This is not the end of the story,” promised Health and Human Services Secretary Tommy Thompson, saying a full ban was still possible and the new FDA actions would serve to build the case. “Throughout America, there continue to be tragic incidents that link dietary supplements containing ephedra to serious health problems.”

Thompson advised people, especially athletes or fitness buffs, not to take the herb — advice that comes two weeks after the latest high-profile death of an ephedra user, Baltimore Orioles pitcher Steve Bechler.

“I would not take this, I would not give it to my family and I don’t know why anyone would take these products,” Thompson said, pointing to a new review of ephedra by the Rand think tank that found it does nothing to enhance sports performance and causes only temporary loss of a few pounds.