WASHINGTON — With millions of its cars still under recall but not yet repaired, Honda Motor said on Thursday it was beginning an advertising campaign aimed at persuading owners to get them fixed.

The cars have faulty airbags made by the Takata Corporation, the Japanese auto supplier, where the inflater can explode, sending metal shards flying into the passenger cabin. At least six deaths worldwide have been linked to the defect, all in cars made by Honda.

The company said its campaign would involve newspaper, radio and social media ads focused on 11 high-humidity states and American territories, where the company says it believes the risk is greatest. About 6.2 million Honda vehicles in the United States have been subject to the Takata recall, and as of this month 14 percent of the inflaters requiring replacement have been repaired.

Honda acted as pressure on Takata increased on Capitol Hill. The Senate Commerce Committee sent a letter on Thursday to the company’s chairman demanding that documents requested by the committee last year be immediately turned over.