The construction company building the new Vikings stadium and the group responsible for overseeing its operation are in a dispute over $15 million.

M.A. Mortenson Company says it shouldn't be on the hook for that money, and is requesting mediation with the Minnesota Sports Facilities Authority, MPR reports.

Mortenson says the extra work came from changes that the MSFA ordered, the Business Journal notes.

The MSFA, in a statement on its site, argues the construction agreement includes a guaranteed maximum price – meaning any risk of cost disputes would be the responsibility of Mortenson.

Arbitration could come if the sides can't come to an agreement through mediation.

The sports facilities authority was created by the legislature in 2012 to oversee the design, construction and operation of U.S. Bank Stadium, its website says. Its next meeting is Aug. 21.

In June, the authority's treasurer Duane Benson abruptly quit after a public falling out with its chair. On his way out, he told the Star Tribune the cost of the stadium could be $35-$50 million over budget.

Michele Kelm-Helgen and Ted Mondale, who head the authority, said that wasn't the case, and any overruns would be covered by the $29 million contingency fund, the paper reported.