Eleven Democratic members of Congress from Illinois are criticizing the Biden Administration’s decision to restrict who can get vaccinated against COVID-19 at the United Center.

The letter sent Friday came as Chicago’s mayor expressed wary optimism that the city would have the vaccine supply necessary to meet President Joe Biden’s directive that all adults in the country be eligible for a vaccine starting May 1.

The letter from the Illinois U.S. representatives is in response to federal officials’ decision to restrict who can get vaccinated at the United Center. Right now, the only people eligible to book the limited available appointments at the state’s largest mass vaccination site are those living in five Chicago ZIP codes, seniors aged 65 and over, frontline essential workers and people 16 and older with certain underlying health conditions.

The Federal Emergency Management Agency restricted who can get their shots at the sports arena after early appointments got snatched up mostly by suburbanites – not by the Chicagoans living in communities of color that have been hardest-hit by the pandemic.

All told, the city public health officials say they want 60% of appointments at the sports arena to go to Chicagoans, with 30% going to suburban Cook County residents and 10% to Illinoisans who live elsewhere. But as of right now, there has been no publicized way for non-Chicagoans to sign up.

Once vaccinations ramp up, officials estimate up to 6,000 shots per day could be administered at the United Center. And the Illinois representatives bristled that more of their constituents can’t take advantage of that.

“Pockets of vulnerability exist all across our state,” the 11 Democrats wrote to Robert Fenton, acting administrator for FEMA. “Restricting these populations from seeking appointments at the United Center Federal Mass Vaccination Center is a departure from the site’s initial message of ensuring all underserved Illinoisans have access to COVID-19 vaccines.

“Moving forward, we respectfully ask you to continue to ensure future decisions on eligibility be fully considered and communicated with all vulnerable Illinoisans – including those beyond Chicago,” they wrote.

The letter was signed by U.S. Reps. Brad Schneider, Jan Schakowsky, Danny Davis, Sean Casten, Robin Kelly, Bill Foster, Jesus Chuy Garcia, Raja Krishnamoorthi, Bobby Rush, Mike Quigley and Marie Newman.

“FEMA is committed to the equitable distribution of vaccines,” FEMA’s Acting Regional Administrator, Kevin Sligh, said in response to the letter. “The decision to change course on registrations had to be made quickly, because delaying the decision would only have ensured that the most socially vulnerable Illinoisans would be excluded from this particular effort.”

Meanwhile, President Joe Biden’s call to make every adult in the country eligible for a COVID-19 vaccine by May 1 received a warm reception from Illinois Gov. JB Pritzker, who expressed optimism that Illinois could beat that goal.

With the state administering more than 100,000 shots in each of the past three days, Pritzker said he has confidence the federal government could continue to supply the state with enough vaccine that Illinois could expand eligibility for every adult before May 1.

“I’m excited about the fact that we’ll be able to get to more and more people across the state of Illinois, and I’m confident that not just by May 1, but maybe even a little bit earlier, we could open up to everyone in the state,” Pritzker told reporters Friday.

But Biden’s announcement was met with wariness from Chicago Mayor Lori Lightfoot, who manages the city’s supply of vaccines separate from the rest of the state of Illinois.

During a televised interview with CNN Friday morning, the mayor said she doesn’t want to “create expectations” that every Chicago adult will be vaccinated by May 1. Biden only said every state must make adults eligible to get vaccinated by that date – not that every adult is guaranteed to get a shot by then.

Still, Lightfoot said it all depends on public outreach — continuing to convince people that getting vaccinated is imperative — and a reliable supply of vaccines.

“We don’t want to create expectations that we can’t fulfill,” Lightfoot said in the interview, as she expressed frustration with the lack of support from former President Donald Trump’s administration when the first round of vaccines were being doled out. “So ramping up the vaccine production is crucial.”

Lightfoot said under the Trump administration, “we were lurching from week to week, really not knowing how much vaccine we were going to get.” The mayor added that the Biden Administration’s efforts to give a “three week look-ahead” on vaccine distribution will make it easier for the city to build up its distribution plan.

She also noted the new Johnson & Johnson vaccine, which only requires one dose, has made a significant impact in the city’s efforts to get eligible adults vaccinated.

The city is still currently focused on vaccinating people over the age of 65 and frontline essential workers, while the state has broadened eligibility to those who have certain health conditions that could complicate their recovery if they were to be infected with the virus.

A WBEZ analysis finds that 1.67 million Chicago adults who are eligible for the vaccine have yet to get a shot in the arm. Statewide, the number of adults who haven’t gotten a shot is 7.4 million.

On Friday, state public health officials announced 54% of Illinois residents who are 65 and older have been vaccinated.

Tony Arnold covers state politics and Claudia Morell covers city politics for WBEZ. Follow @tonyjarnold and @claudiamorell.Reporter Becky Vevea contributed.