MARANA, Ariz. (AP) -- Just when the patent lawsuit between Acushnet and Callaway was getting closer to resolution, both companies filed another round of lawsuits against each other Tuesday that could take two more years to settle.

Acushnet, parent company of Titleist and its Pro V1, already is appealing a verdict that its previous Pro V1 model infringed on four patents owned by Callaway. Titleist says the U.S. Patent & Trademark Office has found the Callaway patents to be invalid, which will be considered in the appeal.

Meanwhile, Titleist introduced a 2009 version of the Pro V1 this year that it said was outside the patents in question.

In the latest court battle, Callaway filed another lawsuit claiming the new Pro V1s still infringe on Callaway patents. Moments earlier, Titleist filed a separate lawsuit in the same federal court in Delaware claiming Callaway has infringed on nine patents with its Tour i and Tour ix golf ball.

"It is regrettable that one of our competitors would rather compete in the courtroom than in the pro shop," said Joe Nauman, Acushnet's executive vice president of corporate and legal affairs. "However, we are committed to seeing these matters through to appropriate conclusions."

Steve McCracken, chief administrative officer for Callaway, said he expects to win the latest round of lawsuits.

"As long as Titleist, or any competitor, continues to introduce products that we believe infringe our patents, we will continue to seek relief in the courts," McCracken said.

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