The owners of the Major League Soccer (MLS) expansion franchise the Minnesota United are in talks about playing games at U.S. Bank Stadium — and it has left the stadium's primary tenant, the Vikings, crying foul and threatening to sue.

United owners and the Minnesota Sports Facilities Authority (MSFA), the agency that manages the $1.1 billion building, have been in discussions about an exhibition game — and perhaps more — at the stadium. But the Vikings say they are being shut out of the discussions in violation of state law and the stadium's use agreement.

"First, it's clear Minnesota United can't play at U.S. Bank Stadium without our consent," Vikings executive vice president Lester Bagley said. "We invested $609 million to make this building soccer-ready and make it a great fan experience."

The Vikings say the 2012 legislation that got the stadium built gave them five-year exclusive rights to bring an MLS team into the building.

Michele Kelm-Helgen, chairwoman of the MSFA, said the Vikings have a right to "establish" an MLS team at U.S. Bank, but the team has no say in whether the Minnesota United play an "exhibition" game at the stadium.

A Minnesota United spokesman, however, indicated the talks went well beyond a single exhibition game and included the possibility of home games at the stadium.

While U.S. Bank Stadium was under construction, Vikings owners Mark and Zygi Wilf tried to lure an MLS expansion franchise into the building. But the Wilfs lost out to a rival group led by former UnitedHealth executive Bill McGuire, Twins owners Bob and Jim Pohlad, Wendy Carlson Nelson, who is on the board of the Carlson Cos. and Glen Taylor, who owns the Minnesota Timberwolves, the Star Tribune and other businesses.

In 2015, when MLS Commissioner Don Garber announced the decision to go with the McGuire group, he praised their plan for a "downtown, outdoor, soccer-specific stadium, 20,000 seats, playing on grass." In other words, the MLS didn't want to play in the Vikings' 66,000-plus seat football emporium with a giant roof and synthetic grass.

Team will open at TCF

In August, the St. Paul City Council approved a plan to build a $150 million, 20,000-seat soccer stadium in the Midway area of St. Paul, although construction hasn't begun. The Minnesota United is set to play 2017 and part of 2018 at TCF Bank Stadium at the University of Minnesota.

About six weeks ago, McGuire contacted Kelm-Helgen, according to United spokesman Eric Durkee.

McGuire asked "in general about opportunities to play home games in U.S. Bank Stadium. There has been no discussion of specific dates or whether we would host MLS game or friendlies," Durkee said, adding that the United was interested in general availability, price and field alignment.

"It's certainly possible that we'd look at playing games at U.S. Bank Stadium whether due to snow or wanting to be able to draw a larger crowd for big games," Durkee said.

To Durkee's knowledge, United has not received a definite response from anyone at this point.

Lawyers for the MSFA and the Vikings have exchanged sharp letters. The Vikings have threatened to sue to enforce what they believe are their rights in the use agreement.

Kelm-Helgen said the terms of a soccer game have not been finalized, but the MSFA has the full legal right to host an exhibition game without consent from the Vikings.

In a letter Wednesday to Vikings counsel Karin Nelsen, MSFA attorney Jay Lindgren said the stadium use agreement doesn't prevent an exhibition match. He also dismissed the Vikings' "threats of litigation," saying the team has no legal basis to stop it.

But Bagley said that up until recent weeks, the Vikings and the MSFA agreed on the soccer policy. "They knew what the language intended," he said of the legislation and the use agreement. "We were surprised when they interpreted [it] differently. We've been good partners."

It's unclear how the disagreement will be resolved.

Sen. Julie Rosen, R-Vernon Center, was the author of the stadium bill and said the legislation is "absolutely clear" that the Vikings have an exclusive right to bring in an MLS team to U.S. Bank Stadium in any scenario.

Kelm-Helgen said, "The Vikings have clearly not established an MLS team at the Stadium, but they still have the legal right to attempt to do so. ... We're just doing our job of bringing high-quality events to the stadium."

Staff Writer David La Vaque contributed to this report.

Rochelle Olson • 612-673-1747

Twitter: @rochelleolson