ST. PAUL, Minn. -- The public authority overseeing Vikings stadium construction on Monday asked the Minnesota Supreme Court to make plaintiffs who sued to stop the project post a $50 million bond to show they could cover damages if they lose.

The Minnesota Sports Facilities Authority filed a motion to intervene in the lawsuit brought by former Minneapolis mayoral candidate Doug Mann and two others. His lawsuit challenges the constitutionality of the state's stadium funding plan and has already delayed a $468 million bond sale.

State officials warn the delay could stall the project's timeline and add costs. A spokesman for the state budget agency says government legal costs will have to come from stadium funds.

The authority's chairwoman said the lawsuit also threatens a major downtown Minneapolis development near the stadium.

The authority asked the state Supreme Court to hear its motion Thursday.

Mann said Monday he has not been served with any paperwork yet.

"I think it's an act of desperation," Mann said. "This is not unexpected. My guess is they're afraid they're going to lose."

Mann filed the challenge with the Supreme Court on Friday. He and two others asked the state's high court for a restraining order to block the bond sale, saying the financing arrangements were designed to circumvent a city charter provision that would have triggered a referendum.

Mann said earlier he believes that Minneapolis voters should have been allowed to decide whether to finance the stadium and that the bond sale violates the state constitution because city sales tax money would be used to finance a state debt. A Hennepin County judge dismissed an earlier challenge from Mann in November.

The bonds will cover the state's and city's share of the $1 billion stadium on the site of the old Metrodome. The Vikings are paying for the rest.

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