U.S. President Donald Trump is eyeing Afghanistan's mineral wealth to help pay for a 16-year war and reconstruction efforts that have already cost $117 billion. But investors who have studied the country, one of the world's most dangerous, say the idea is a pipe dream.

Trump was to lay out his long-awaited strategy for Afghanistan in a prime-time television address to the American people on Monday night, the White House said Sunday, with a modest increase in U.S. troops possible.

Ever since a United States Geological Survey study a decade ago identified deposits later estimated to have a potential value of as much as $1 trillion, both Afghan and foreign officials have trumpeted the reserves as a likely key to economic independence for Afghanistan.