MINNEAPOLIS — The Minnesota Vikings said Friday they will increase their contribution to a downtown stadium to more than $500 million to make sure the project has everything they want as construction of their new home rapidly approaches.

The team had been scheduled to pay $477 million of the stadium’s nearly billion-dollar cost. But bids coming in higher than expected made the Vikings worry about losing distinctive design features and having to settle for less than top-end technology, such as ribbon scoreboards and high-definition televisions in concourses.

“The only options were to whack the project, cut significantly back in the building, step back and redesign and try to redraw to a lower number or have the team put in more money,” team vice president Lester Bagley said. “That’s what our owners decided to do.”

Reconfiguring the stadium design to significantly cut costs would have delayed the project by a year or more, officials said.

The stadium cost could now top $1 billion — with $498 million in public money — if builders need to use the entire pot of available money. Legislators approved the new stadium to replace the Metrodome out of concern that the Vikings could leave the state.

Ceremonial groundbreaking is set for early next month, with the projected opening in 2016. John Wood, a senior executive at Mortenson Construction, said fences will go up around the Metrodome next week and heavy equipment will be moved in. Orders for steel for the new stadium will go in soon, with some specialized beams for the see-through roof coming from Luxembourg.

The Vikings play their last game in the Metrodome on Dec. 29, ending a three-decade run for the Teflon-topped stadium that has hosted the Super Bowl, the Final Four, the World Series and countless monster truck rallies. A three-month demolition phase will start in mid-January.

The Vikings were closing on their private financing Friday. They are using loans, seat license sales, a naming rights deal and other private revenue streams.

The Vikings’ extra contribution comes in the form of a letter of credit guaranteed by owner Zygi Wilf, a real estate mogul. The contingency would be tapped if construction officials can’t find savings elsewhere.

But the attempt to shave costs has been unsuccessful so far.

Minnesota Sports Facilities Authority chairwoman Michele Kelm-Helgen said the rising costs are a sign of an improving economy.

“The good news: Construction is up. The bad news is construction is up and some of our bids were coming in higher than anticipated,” she said.

Aside from the Vikings $26.4 million letter of credit, the team is also forgoing $15 million in breaks it was due to receive as part of a deal to play two seasons at the University of Minnesota’s on-campus stadium during construction.

Wood said builders will still look for cost savings as the project proceeds over the next three years. But he noted that 16,000 man hours went into designing and pricing out stadium features, so planners are confident they will keep to the budget, including the contingency accounts.

“It’s there to spend,” he said.

Overall, the materials and labor for the stadium will cost $763 million. The remainder of the stadium price tag goes for things like architecture, legal fees and insurance.