MAST Travel Network, a consortium with about 200 Midwest travel agencies, said it will no longer have a preferred-provider arrangement with Carnival Cruise Lines after Jan. 1.
MAST said its board of directors voted unanimously to drop Carnival as a preferred vendor.
MAST President John Werner said Carnival's level of marketing and sales support no longer justified the preferred status, which MAST has maintained since Carnival's early years in business.
"Carnival's business strategies have changed, and for MAST, those strategies no longer fit our business model," he said.
In a statement, Carnival sales vice president Joni Rein said Carnival understands and respects MAST's position.
She said each year, including for 2013, Carnival reviews and changes criteria for compensating travel agents. "These changes in criteria do not affect the majority of U.S. travel agents," she said.
In particular, Rein said, "Carnival will continue to have a significant U.S. marketing co-op program in 2013, as we have in prior years."MAST is the second group in recent weeks to drop Carnival as a preferred supplier. Signature Travel Network made a similar announcement earlier this month.
Follow Tom Stieghorst on Twitter @tstravelweekly.
Update: This report was edited late Thursday morning to add Carnival's statement.