SEATTLE — A group proposing to build an arena for NBA and NHL use in the Seattle’s Sodo District offered Thursday to renovate KeyArena into a mid-sized concert venue.

The group, led by entrepreneur Chris Hansen, wrote on its Sonics Arena website that the plan would split KeyArena in half by creating a 6,200-seat indoor concert venue on one side and a 3,000-seat outdoor covered amphitheater.

There also would be a 500-seat theater added. Hansen’s group said the KeyArena re-development would occur after a Sodo arena is built. Hansen’s group estimates the cost to be between $90 million and $100 million.

“We believe these new venues would be a perfect complement to the larger SoDo Arena’s 16,000-21,000-seat flexible capacity,’’ Hansen’s group said on the website. “It would also address the City’s need for a mid-size concert venue and amphitheater. We believe the combination of a completely new and modern SoDo sports arena and the new Seattle Center Venues is vastly superior to a single, site-challenged sports venue at KeyArena.’’

The timing of the announcement comes as the city prepares to release a draft Memorandum of Understanding (MOU) on a proposed $564 million renovation of KeyArena for NBA and NHL use and as a major concert facility.

The Los Angeles-based Oak View Group, led by Tim Leiweke and Irving Azoff, has offered to renovate the arena “on spec” ahead of securing teams and would help finance it via concerts in the short term.

Hansen’s group has said it would build a $600 million Sodo arena only after securing teams. 

But he has yet to partner with any prospective NHL owners, and the NBA appears unlikely to expand or relocate teams for several years.

The Sodo group has asked the city to vacate a portion of Occidental Ave. South it needs to complete its arena land acquisitions. 

But the city has put off exploring that request until it deals with the KeyArena MOU, which the city council has been asked to finalize by year’s end ahead of an expected NHL expansion announcement.

The idea of a split-venue KeyArena remodel was first proposed for sports and concerts in a report by the AECOM architectural firm that studied future uses for the city-owned building. 

Unlike other rejected future uses, the split-model facility was the only one in which KeyArena was projected to have a shot at breaking even financially on a year-to-year basis.

But the price tag of that option was pegged at roughly $150 million. At the time, AECOM expressed doubts that any private entity would want to fund such a renovation, given the cost and the relatively low returns.

Instead, the full-fledged renovation for NBA and NHL was seen as the only way to attract private investors to foot the bill and allow the city to continue seeing profits from operations.