According to new commercial-satellite imagery obtained exclusively by Newsweek, Pakistan is aggressively accelerating construction at the Khushab nuclear site, about 140 miles south of Islamabad. The images, analysts say, prove Pakistan will soon have a fourth operational reactor, greatly expanding plutonium production for its nuclear-weapons program.

“The buildup is remarkable,” says Paul Brannan of the Institute for Science and International Security. “And that nobody in the U.S. or in the Pakistani government says anything about this—especially in this day and age—is perplexing.”…

Although the White House declined to comment, a senior U.S. congressional official who works on nuclear issues told Newsweek that intelligence estimates suggest Pakistan has already developed enough fissile material to produce more than 100 warheads and manufacture between eight and 20 weapons a year. “There’s no question,” the official says, “it’s the fastest-growing program in the world.”