Be wary of stocks outside the US: Bogle

Investors should buy American equities over international stocks because the U.S. economy already holds a huge stake in global business, Jack Bogle, founder of The Vanguard Group, said on Monday.

"You don't need to do international investing because the U.S. is an international economy," Bogle told CNBC's "Closing Bell."

Jack Bogle

Peter Foley | Bloomberg | Getty Images

American investors putting their money abroad face a "currency risk" as the dollar strengthens against various currencies, Bogle said. The euro, for instance, hit a 11-year low against the dollar last week before steadying on Monday.

Read MoreHave no fear: Behind the VIX plunge

Exchange rates make Bogle wary of putting too much weight in stocks abroad.

"Don't go over 20 percent in non-U.S. securities because you earn your money in dollars, you spend your money in dollars, you save your money in dollars," he said.

Read MoreETFs on way to $5 trillion in assets