The agreement to bring the America’s Cup regatta to San Francisco was modified in ways that could result in more costs to The City than previously anticipated, according to a budget analyst’s report released Thursday night.

The report calls into question the validity of the agreement, one of Mayor Gavin Newsom’s final acts before leaving office.

On Dec. 14, the Board of Supervisors approved a draft of the host-city agreement, stipulating that city and Port of San Francisco officials could continue negotiating as long as the costs to The City were not changed.

On Dec. 31, hours before the New Year’s deadline, the Mayor’s Office announced that a final agreement had been inked.

City officials said that while the final agreement had been modified, the changes did not affect the cost-benefit ratio.

However, Budget Analyst Harvey Rose’s report said that “some of the modifications represent material changes” from the supervisors’ draft, and those changes “could have a material impact on Port revenues and costs.”

The changes include a more lenient method of assessing the base rent the America’s Cup team will pay for land it will gain rights to after the lease, and the removal of a requirement that the team pay the Port part of its profit if it develops condominiums.

Port official Brad Benson, who helped negotiate the agreement, said he was “not concerned about this [report] having a negative effect on The City’s efforts for the America’s Cup,” adding that the City Attorney’s Office approved every change. He said the negotiating team was “very mindful about the board’s direction” not to increase The City’s liabilities or obligations.

kworth@sfexaminer.com