The Environmental Protection Agency announced a new program Tuesday for reducing lead in drinking water, setting standards that could eventually force some cities to replace old lead pipes.

"This rule will give us the most stringent drinking water standards for lead in the entire world," EPA Deputy Administrator Henry Habicht said at a news conference.Lead is a poison that can produce high blood pressure in adults. Its chief danger is to children, because small amounts can interfere with development of the brain.

The agency estimates that its regulations, years in preparation, would reduce blood lead concentrations in 600,000 children below the "level of concern" set by the Centers for Disease Control.

But environmentalists were dismayed, saying EPA failed to set an enforceable limit. Instead, there is an "action level" for lead of 15 parts per billion. Water systems that exceed the level in 10 percent of high-risk homes monitored for lead will be required to take steps to reduce lead content.

"This is a major disappointment," said Karen Florini, a senior staff attorney for the Environmental Defense Fund. "EPA didn't set an actual standard that limits lead in drinking water. The other problem is the glacial pace of the compliance schedule."

Officials described the regulations as their most important against lead since they began proceedings to reduce lead in gasoline in 1976.

EPA's new program will require water systems to monitor tap water in "high-risk" households - those with lead service pipes leading in from the main, or recent lead solder on copper pipes.

If 10 percent of these households show concentrations of 15 parts per billion in tap water, the supplier will have to undertake "optimal corrosion control."