The plan was unveiled by Seattle Mayor Mike McGinn and King County Executive Dow Constantine, who said the facility has been proposed by a private investment group headed by Seattle native Christopher Hansen, a hedge fund manager in San Francisco.
"The Seattle Mariners are excited about this afternoon's announcement and the possibility of having NBA and NHL teams coming to the Seattle area," the team said in a release. "From our perspective, it is all about the fans and the community.
"We aren't familiar with the details, but are ready to participate in the public process to make this a 'win' for the fans and to realize the many potential benefits for the region. It is too early for us to make any further comments."
Seattle has been without an NBA team since the Sonics moved to Oklahoma City in 2009.
The proposed arena would be located just south of Safeco Field and $290 million of the cost would come from Hansen, with another $200 million from city and county financing that doesn't require new taxes, according to McGinn and Constantine.