WASHINGTON — Having been rebuffed privately by President Obama last week, Prime Minister Benjamin Netanyahu of Israel took to the airwaves in the United States on Sunday to warn that Iran was only six or seven months from having “90 percent” of what it needed to make an atomic bomb.

Mr. Netanyahu received sharp criticism at home and abroad for similar remarks last week, which were widely seen as an effort to put pressure on Mr. Obama to act more forcefully against Iran. And yet, less than two months before Election Day, he turned to the weekly platform for American politics — the Sunday morning political talk shows — to make his case more urgently and specifically than ever to a wider American audience.

He repeated his warning that the only way to stop Iran was for the United States to draw a distinct “red line” on that country’s nuclear activity and declare that crossing it would trigger military intervention. But he also offered his most explicit description to date of the level of nuclear development that he would regard as particularly dangerous: one bomb’s worth of medium-enriched uranium, a level that would take Iran close to a bomb but would still require additional work to make a weapon.

He implied that Iran would cross that line soon. “You know, they’re in the last 20 yards, and you can’t let them cross that goal line,” Mr. Netanyahu said on the NBC News program “Meet the Press,” displaying his familiarity with American football, another Sunday ritual here. “You can’t let them score a touchdown, because that would have unbelievable consequences, grievous consequences for the peace and security of us all, of the world really.”