Oculus VR Inc. signage is displayed at the company's booth at the 2014 Electronic Entertainment Expo (E3) in Los Angeles, California June 11, 2014. REUTERS/Kevork Djansezian

Virtual-reality headset maker Oculus is finally speaking up about its bitter dispute with Zenimax, one of the largest video game companies in the United States. Two months after Oculus announced that it would be acquired by Facebook in a $2 billion deal, ZeniMax accused the headset maker of infringing on the publisher's intellectual property.

ZeniMax says it owns the development work that Oculus chief technology officer John Carmack, a prominent game developer and former ZeniMax employee, contributed to early versions of the Oculus Rift headset. Carmack consulted with Oculus founder Palmer Luckey in 2012, when the device was just a prototype.

In a court filing Wednesday, Oculus strongly rejected that claim. "The lawsuit is nothing more than ZeniMax seeking to correct for a massive missed opportunity through the assertion of meritless litigation," the company said in a copy of the filing provided to The Washington Post.

ZeniMax did not immediately respond to a request for comment.

In the filing, Oculus says ZeniMax has no right to any of the development work that went into the Rift, pointing to comments from Carmack made in 2012, saying the credit for the Rift's invention and development should all belong to Luckey.

Oculus also says a non-disclosure agreement that Luckey signed with ZeniMax in 2012 is not valid because it was never finalized. That agreement, at the center of ZeniMax's suit, gave the publisher "exclusive ownership of the confidential and proprietary information"  to what Carmack did for the Rift.

"[The] parties never finalized the NDA, which omitted key terms defining what use Luckey could make" of material that Carmack, then still a ZeniMax employee, sent him to test the Rift, the filing said.

In the document, Oculus makes clear that it believes ZeniMax is only interested in suing Oculus now because of the Facebook deal.

"There is not a line of ZeniMax code or any of its technology in these or any other Oculus products," the filing said. "ZeniMax never claimed otherwise until the Facebook acquisition" despite having ample time to do so, the company said.