The Miami Dolphins have offered to repay Miami-Dade County for a portion of the public costs of renovating Sun Life Stadium, and to pay millions of dollars in penalties should the team fail to bring major events to South Florida, including four Super Bowls over the next three decades, The Miami Herald has learned.

The Dolphins have told the county they will repay Miami-Dade for the initial share of the renovation costs in about 30 years, but the rebate would not include the debt payments that will likely come with the deal, according to a source familiar with the Dolphins’ offer and a draft term sheet obtained by The Herald.

During meetings last week with NFL owners in Phoenix, the Dolphins shared a confidential report on their ongoing negotiations with Miami-Dade Mayor Carlos Gimenez to bring the issue to a countywide vote, according to an NFL source. The source said the Dolphins revealed they have offered to use private dollars to fund $225 million in construction costs for a renovation now estimated at $389 million, less than the $400 million figure that was the most commonly used estimate for the deal.

That amounts to the Dolphins asking for public money to fund about 43 percent of the construction costs, less than the 49 percent that was initially floated as a starting point by the team. And the Dolphins have offered to go one step further and repay Miami-Dade for the $120 million the county would be expected to put into the renovation, the NFL source said. The remaining $44 million would come from a state sales-tax subsidy.

The new details on the Dolphins’ offer come as the team faces pressure to close a deal with Gimenez and then launch a campaign to win a countywide referendum that would be needed to get the funding plan approved. The Dolphins want to pay for a portion of the renovations with a new $3 million rebate on sales tax it pays the state, as well as with new dollars generated by increasing the taxes charged mainland Miami-Dade hotels to 7 percent from 6 percent.

Last week, the Dolphins announced two concessions initially floated by the county: If state officials agree the team will cover the costs of holding the referendum, and the team will not accept county dollars if the NFL does not award South Florida the 50th or 51st Super Bowls when league owners convene May 22.

The term sheet obtained by The Herald also included details on a repayment plan. Under those terms, the Dolphins would repay the county $120 million in 2043, after the end of a 30-year deal covered by the agreement. The terms do not include an adjustment for inflation, and would not return to Miami-Dade any of the interest expense the county would incur to repay $120 million in bonds borrowed using the revenue created by the higher hotel tax.

According to the term sheet, the Dolphins would be bound by the agreement even if the team is sold.

The team would pay the county a penalty at the end of the 30-year agreement if the Dolphins do not deliver a minimum number of events at the stadium, including at least four Super Bowls, four college football championship games and 22 soccer matches. For example, the penalty for not landing a Super Bowl would be $15 million. The NFL source said the team would pay up to $100 million in penalties.

The Dolphins would also sign a non-relocation agreement, agreeing to stay in Miami until 2043. The stadium renovation would be completed by September 2015, the NFL source said.