June 28 (Reuters) - Mattel (MAT.O) has asked the U.S. Trademark Office to reject British fashion house Burberry's (BRBY.L) proposed "BRBY" trademark, arguing it is likely to sow confusion with Mattel's famous Barbie brand.

The toymaker said in a Monday filing that the "BRBY" mark for Burberry clothing, bags and other products would mislead consumers into thinking they were associated with Mattel's Barbie dolls and related merchandise and would dilute its brand.

Representatives for Mattel and Burberry did not immediately respond to requests for comment on the Monday filing.

Mattel "certainly has a point that BRBY could phonetically sound like Barbie," said Josh Gerben, a trademark lawyer who first posted the filing to Twitter on Wednesday. "Burberry is going to have a strong counterpoint that these initials could very much be associated with its name, especially in the context of how the mark is likely to be used."

Similar disputes are often settled with guidelines and limitations on the trademark's use, said Gerben, who is not involved in the case.

Mattel said it uses its world-recognized "Barbie" mark in many fields outside of the popular dolls it introduced in 1959. It cited federal trademarks for products including clothing, jewelry and cosmetics, as well as a highly-publicized live-action "Barbie" movie opening next month.

Burberry applied for a federal trademark for "BRBY" last year. Mattel said "BRBY" and "Barbie" are "visually similar" and "phonetically identical," and argued consumers could view "BRBY" as "a subset or expansion of the Barbie trademarks."

Mattel in April reported losses for the first quarter of 2023 based on increased production costs and a 21% drop in net product sales. It said at the time that it expected its financial situation to improve later this year. It said its worldwide gross billings for Barbie, which represent amounts invoiced to customers, fell 41%.

The case is Mattel Inc v. Burberry Ltd, Trademark Trial and Appeal Board, Opposition No. 91285723.

For Mattel: Sharoni Finkelstein of Venable

For Burberry: Andrea Calvaruso of Kelly Drye & Warren