Kansas City, Mo. ? Downtown boosters launched a campaign Tuesday to build a new, $357 million baseball stadium for the Kansas City Royals downtown, funded by a three-eighths of a cent county sales tax.

The plan being pushed by the Downtown Council calls for a countywide sales-tax election in April that would pay for a 40,000-seat downtown ballpark and upgrades to Arrowhead Stadium, home of the Kansas City Chiefs.

An April election already is in the works to fund improvements at Kauffman and Arrowhead, which are needed to prevent Jackson County from defaulting on a lease agreement for the two facilities.

“Yes, Kauffman is nice,” Downtown Council chairman Jon Copaken told an audience Tuesday. “But nice is not a good enough reason for a $300 million county investment.”

Jackson County officials largely oppose the downtown plan, arguing that Royals fans prefer the team play at Kauffman Stadium – and that the proposal pitched Tuesday was an attempt to derail the effort to upgrade Kauffman Stadium.

Kansas City Mayor Kay Barnes noted Royals owner David Glass has said repeatedly he preferred to stay at Kauffman Stadium.

“I think it is important that we get behind the (Royals) ownership and support whatever initiative that Jackson County may put on the ballot in April,” she said. “Saving the franchise, to me, is the bottom line.”

Already under construction downtown is the new Sprint Center, which is expected to play host to an indoor football team and potentially either a professional basketball or hockey franchise.

John Fairfield, a downtown ballpark proponent and member of the City Council, said a new stadium “would be the icing on the cake of all the redevelopment we’ve done downtown.”

But Mike Smith, chairman of the Truman Sports Complex Authority, said voters preferred taking the less-expensive route and revamping Kauffman Stadium at an estimated cost of around $245 million.

“Leave Kauffman where it is and quit worrying about bringing baseball downtown and worry about bringing development to Kauffman,” he said.