TUCSON, Ariz. (AP) — A plan to establish a large federally supported mass vaccination site in metro Tucson is being shelved and Pima County instead is now asking for it in mobile form.

Following weeks of discussions, state and federal officials did not come to terms on an agreement for authorizing and running the proposed mass vaccination site, officials said Tuesday.

The county is now pivoting to ask the Federal Emergency Management Agency for mobile sites capable of providing about 300 shots daily to reach populations that could use help getting vaccinated, said County Administrator Chuck Huckleberry.

“It’s an inconvenience for a variety of reasons because they don’t have the technology, they don’t have the time, because they don’t have the wherewithal, mobility issues, language barriers," said Dr. Francisco Garcia, the county's medical officer. “We need to decrease those barriers."

The mass vaccination site would have been operated by FEMA and could have vaccinated up to 6,000 people daily.

The plan's apparent demise comes as existing state-run mass vaccination sites across the state have thousands of appointments available. Those sites include one on the University of Arizona's campus in Tucson.

State and county officials said sticking points in the talks on the proposed FEMA mass vaccination site included the state's insistence it have a liability shield.

Without the shield, “we felt it put the state at a significant liability,” said Dr. Cara Christ, director of the state Department of Health Services.

FEMA spokesman Robert Barker told The Arizona Republic that talks continued on FEMA's support for Pima County. The agency “may have an announcement shortly," he said Tuesday in an emailed statement.

In another development, the state Department of Health Services on Wednesday reported 649 additional confirmed COVID-19 cases and six deaths, increasing the state's totals to 855,804 cases and 17,199 deaths.

The number of infections is thought to be far higher than reported because many people have not been tested, and studies suggest people can be infected with the virus without feeling sick.

More than 2.7 million people in Arizona — or 38.5% of the eligible population — have received at least one dose of a COVID-19 vaccine. Close to 2 million have been fully vaccinated.

Arizona's vaccination rate has slowed compared to other states, according to Dr. Joshua LaBaer, executive director of Arizona State University’s Biodesign Institute. He is hopeful more people are planning to get shots now that anyone as young as 16 can receive it.

The vaccines are also the best bet to combat more contagious strains like the variant that originated in the United Kingdom and has been found in Arizona. There have been reports that the highly transmissible U.K. variant is showing up more in younger people including children, LaBaer said.