SAN FRANCISCO (AP) -- San Francisco on Thursday sued Oakland after officials there voted in favor of changing the name of the city's airport to San Francisco Bay Oakland International Airport, saying the change will cause confusion and is already affecting its airport financially.

Last week, the Board of Commissioners for the Port of Oakland voted unanimously to move forward with the name-change and scheduled a second vote for final approval on May 9. The airport is currently called Oakland International Airport.

"We had hoped Oakland would come to its senses, but their refusal to collaborate on an acceptable alternative name leaves us no choice but to file a lawsuit to protect SFO's trademark," San Francisco City Attorney Chiu said in a statement.

San Francisco is asking the court to prevent Oakland airport from moving forward with its name-change and rule that the new name violates San Francisco International Airport's trademark.

"The renaming plan appears intentionally designed to divert travelers who may be unfamiliar with Bay Area geography and lead them to believe OAK has a business relationship with SFO, which it does not," Chiu said, adding that the renaming would be particularly confusing for international travelers who don't speak or read English.

Oakland airport officials said they plan to implement the name-change and defend their right to do so in court.

"OAK's proposed renaming does not infringe upon SFO's mark," the Port of Oakland said in a statement. "We will vigorously defend our right to claim our spot on the San Francisco Bay."