Performance apparel and footwear maker Under Armour has filed a lawsuit that claims sportswear giant Nike is infringing its I Will trademark.

The lawsuit, which was filed in the district court of Maryland in Baltimore, said Nike launched an advertising campaign for its performance apparel, footwear, accessories and sporting goods last year, which repeatedly uses the phrase "I Will". 

However, Under Armour claims Nike's use of the phrase imitates its "I Will" trademark, which is used for the same types of products.

In a statement sent to just-style, Under Armour said: "The I Will trademark is one of the cornerstone symbols of our company and its products and services, and has been for many years.

"We have initiated a lawsuit against Nike Inc based on its infringement of Under Armour's federally registered I Will trademark.

"We prefer to battle our competitors in the marketplace and on the field of play with our game- changing innovative products, but we will defend ourselves whenever necessary to protect what we've worked so hard to build," the statement added. 

Meanwhile, Nike declined to comment when contacted by just-style on Friday (22 February).