Hillary Clinton's chief campaign strategist met with Colombia's ambassador to the U.S. on Monday to discuss a bilateral free-trade agreement, a pact the presidential candidate opposes.

Attendance by the adviser, Mark Penn, was confirmed by two Colombian officials. He wasn't there in his campaign role, but in his separate job as chief executive of Burson-Marsteller Worldwide, an international communications and lobbying firm. The firm has a contract with the South American nation to promote congressional approval of the trade...