SEATTLE - Seattle officials filed a lawsuit Monday to keep the SuperSonics from leaving town, saying the team’s profitability at KeyArena “has less to do with KeyArena than perhaps the Sonics’ ability to defend the high pick-and-roll.”

The lawsuit was filed in King County Superior Court just a few days after new Sonics chairman Clay Bennett issued a demand for arbitration, seeking to buy out the remainder of the team’s lease unless an agreement on a new arena is reached by the end of October. The complaint asks that a judge force the Sonics to stay through the end of the lease, in 2010.

Seattle City Attorney Tom Carr and former Republican U.S. Sen. Slade Gorton, the city’s legal big gun, said the issue is simple: In exchange for $74 million in renovations to the old Seattle Coliseum in the mid-1990s, the Sonics agreed to play all of their home games there through Sept. 30, 2010.

“The lease is 15 years. We didn’t agree to a 12- or 13-year-lease term,” Carr said. “We simply ask that they keep that agreement.”

Bennett’s Oklahoma City-based ownership group bought the Sonics and the WNBA’s Seattle Storm for $350 million last year, and has insisted that the Sonics need a new, $500 million stadium.

Among the complaints are that KeyArena is the smallest venue in the league and that under the lease agreement the Sonics must turn over too much of their revenue to the city. NBA commissioner David Stern has called the lease the worst of any team in the league.

The arbitration demand states that the team has lost money every year since 1999 — more than $55 million in the last five years alone. It said losses for the fiscal year ending Sept. 30, 2007, will be more than $17 million.

Louie Richmond, a Seattle-based spokesman for Bennett, said he did not have any immediate comment.

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“I don’t think it’s been fully read yet. That’s all I can say,” he said. “I take Mr. Bennett at his word. ... The Sonics ownership’s goal is to get an arena built in Seattle. It always has been.”

Carr and Gorton argued that Bennett’s demand for a new arena was presented so late in the legislative session and required so much public funding that it appeared designed to fail, clearing the way for a move to Oklahoma. The team had offered to pay 20 percent of the cost.

“The city, with the help of some fine lawyers, is standing up to a pro sports team,” Carr told a news conference. “Too often, pro sports teams have run over local governments.”

The two noted that the Sonics made money at KeyArena until 1999, and Carr suggested it’s the quality of the team, not the quality of the venue, that is the problem.

“The issues with the Sonics’ profitability at KeyArena have less to do with KeyArena than perhaps with the Sonics’ ability to defend the high pick-and-roll,” Carr said.

Gorton, a lawyer who sued the American League to help Seattle land the Mariners and who was instrumental in preventing the departure of the Seattle Seahawks under former owner Ken Behring, said at the news conference that while many disputes that could arise under the lease are subject to arbitration, the duration of the lease is clearly excluded.