Private equity firm MatlinPatterson has outbid Nokia Siemens (NSN) for Nortel's wireless assets with a $725 million offer.
But Canada-based smartphone firm RIM claims it was unfairly excluded from the bidding and would have offered up to $1.1 billion.
Nortel, the networking vendor once worth $250 billion, filed for Chapter 11 bankruptcy protection in January.
MatlinPatterson, which represents bondholders owning $400 million in Nortel debt, said it would operate the wireless division as a standalone business if its offer is accepted.
It said its offer provided a "superior outcome" to NSN's $650 million bid and would take steps to acquire other Nortel assets as they became available.
"MatlinPatterson has been an investor in Nortel for some time now, we are unwilling to accept and will actively take steps to prevent a 'fire sale' of Nortel's core assets followed by the wholesale liquidation of the remaining businesses," the company said in a letter to shareholders.
A spokesperson for NSN toldBloomberg the company would assess the bid, but still believes its offer is in the best interest of Nortel employees and customers.
RIM said it had unfairly been excluded from the bidding for the Nortel businesses.
Nortel told the BlackBerry-maker it could only bid for the unit if it agreed not to submit any offers for other Nortel assets for one year. RIM said it had been prepared to bid up to $1.1 billion.
"RIM remains extremely interested in acquiring Nortel assets through a Canadian ownership solution that would [keep] key wireless technologies in Canada and [extend] RIM's leadership in the research, development and distribution of leading edge wireless solutions, but RIM has found itself blocked at every turn," CEO Jim Balsillie said in a statement.
An auction for the assets has been set for July 24.
Nortel declared bankruptcy in January, and has since launched bids to sell both its wireless and enterprise divisions, with Avaya offering $475 million for the latter this week.
The company expects to sell its third business unit, the Metro Ethernet group, by the end of the quarter.