(CBS News) At the United Nations Thursday, Israeli Prime Minister Netanyahu warned that Iran's work to build a nuclear bomb will be irreversible by next summer.That's significant because he's never put a time frame on it before. It looked like a cartoon but it was deadly serious. Netanyahu drew the red line that would trigger an attack on Iran's nuclear program as clearly as it has ever been drawn.
"A red line should be drawn right here," Netanyahu said, literally drawing a red line on a bomb diagram. "Before, before Iran completes the second stage of nuclear enrichment necessary to make a bomb."
That second stage is taking place at an underground facility near the holy city of Gum, where Iran is enriching uranium to a 20 percent level of purity -- one step away from the 90 percent needed to build a bomb.
According to the latest report by U.N. inspectors, Iran has about 200 pounds of 20-percent uranium -- roughly two thirds of what it would need to build one nuclear device. At the current rate of enrichment, Iran would have enough 20-percent uranium for one bomb in about 10 months -- or as Netanyahu told the U.N. -- by next spring or summer. After that, it would take just a few months more to enrich the uranium to the 90-percent bomb grade level.
Netanyahu said Iran's nuclear program must be stopped before then, "before Iran gets to a point where it's a few months away or a few weeks away from amassing enough enriched uranium to make a nuclear weapon."
But as Defense Secretary Panettaearlier this month, the U.S. has a different red line.
"When they make the decision to go ahead and build a nuclear weapon, that, for us, is a red line," Panetta said.
U.S. intelligence does not believe Iran has made that decision yet, but Netanyahu said it is too dangerous to rely on intelligence to detect a decision made in secret, which is why he set his red line on something he can see -- uranium enrichment.
Panetta used to worry that Israel might strike Iran as early as this past spring. Judging by what Netanyahu said Thursday, the time to worry will be next spring.