In an interview with the Pittsburgh Tribune-Review, Hoffa called the junior senator from Illinois "the best" presidential candidate for organized labor, citing Obama's opposition to the North American Free Trade Agreement.

Hoffa said NAFTA was enacted as the result of "corporate greed" that shows "total disregard for workers."

Hoffa was campaigning in the Keystone State ahead of its April 22 primary. He said Obama, whom the union endorsed Feb. 20, leads Sen. Hillary Clinton, D-N.Y., in delegates and in money raised.

Obama has an "extra charisma," Hoffa told the newspaper.

"This guy is an all-star," he said. "He can fill a basketball arena."