Plans for a U.S. nuclear-power revival have excited uranium investors, stoking demand for shares in companies that produce the fuel.

A classified International Atomic Energy Agency report found Iran, since February, produced 300 pounds of uranium enriched to 60%, a step away from weapons-grade.

The preliminary U.S. proposal came as a confidential U.N. report described an Iranian initiative that had multiplied Tehran’s stockpile of near-bomb-grade uranium.