Nokia Siemens has asked a U.S. bankruptcy court to reject Ciena Corp. (Nasdaq:CIEN) as the winning bidder for the optical networking and carrier Ethernet division of Nortel Networks and suggested it would be willing to pay more.

Nokia Siemens and its partner, One Equity Partners, said Tuesday they would be willing to pay $810 million in cash for the business.

The offer would top the $530 million US in cash plus $239 million US of convertible notes due June 2017 that made up Ciena's winning bid for what was considered one of Nortel's more prized units.

In its filing with the bankruptcy court, Nokia Siemens took issue with the valuation of the convertible note portion of the offer.

Nokia Siemens, with One Equity Partners, said it had offered $770 million in cash during the auction, but Nortel picked Ciena instead.

A Ciena spokeswoman said the company was aware of the objection but declined to comment.

A hearing to approve the sale of the division to Ciena is scheduled for Wednesday.

Nortel has been selling off its divisions after filing for creditor protection in January.

So far, it has sold off several pieces of the business, including its next-generation packet core network component assets to Japanese electronics manufacturer Hitachi Ltd. for $10 million US. It also unloaded its enterprise solutions division to New Jersey-based Avaya for $900 million.