SEATTLE (AP) — The effort to build a new arena in Seattle with the hopes of seeing the NBA return has added a big name: Microsoft CEO Steve Ballmer.

Ballmer will be part of the investment group for both the arena and the acquisition of an NBA franchise, according to a letter sent Wednesday by hedge-fund manager and investment group leader Chris Hansen to King County Executive Dow Constantine and Seattle Mayor Mike McGinn.

“While it was my intention to wait until the local investor group was fully assembled before making any announcement, given the intense community interest and requests from the city and county councils, three members of my investment group have agreed to come forward at this time,” Hansen wrote in the letter, which was obtained by The Associated Press.

That Ballmer is part of the investment group is not a surprise. Ballmer is a longtime basketball fan who regularly sat courtside at SuperSonics games before their departure to Oklahoma City in 2008 and was part of a group that made a last-ditch effort to try to keep the team in Seattle.

At that time, Ballmer teamed with a handful of other Seattle businessmen to offer a renovation of KeyArena. Now Ballmer is throwing his support, and dollars, behind Hansen’s proposal for a $490 million arena to be built in the city’s SoDo neighborhood to house an NBA franchise and which could possibly bring the NHL to Seattle.

Also part of the investment group will be Erik and Peter Nordstrom, members of a prominent Seattle family that owned the NFL’s Seattle Seahawks from 1976-1988. Erik and Peter Nordstrom will also invest in both the arena and a franchise.

“These three gentlemen, like me, are committed to operating the arena and NBA franchise in a way that represents and upholds the values of our community,” Hansen wrote. “They appreciate the role the Sonics played in this community for more than 40 years and see this project as an opportunity to bring that civic asset back to our community.

“They also understand the unique ability of professional basketball to positively affect urban youth. Their participation in the ownership group brings added assurances the business will always be backed by strong local hands and reinforces my commitment that the team will never again leave Seattle.”

In an interview on KJR-AM Wednesday morning, Hansen said he would be the majority owner of any NBA franchise that comes to Seattle and his investment group would include about 10 people.

A memorandum of understanding on the arena was reached between Hansen, Constantine and McGinn last month. That agreement is being debated and reviewed by the Seattle City Council and King County Council, with the expectation of a vote coming later this summer. Both entities would need to approve the agreement for the project to move forward. No construction would begin until after a franchise has been acquired.

The project calls for about $290 million in private investment from Hansen’s group, along with $200 million from the city and county through 30-year bonds. Any franchise that comes to Seattle and uses the arena would be required to sign a non-relocation agreement that would span the life of those bonds.

All construction costs, including overruns, would be paid for by Hansen’s group, along with all environmental studies and permitting. Once that process is completed, most of the public investment is placed on the city. The public investment is capped at $200 million and would come from taxes and revenues generated through the new facility.

So far, the loudest objections have come from the Port of Seattle over concerns for what a third sports facility in Seattle’s SoDo neighborhood would do to a main route for industrial traffic in the same area.

Earlier this week, McGinn delivered a personal message to NBA Commissioner David Stern, saying the city is interested in having the league come back. On Tuesday night before Game 1 of the NBA Finals, Stern said he was encouraged by Seattle’s interest.

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