An increasing number of COVID-19 vaccination sites around the U.S. are canceling appointments because of vaccine shortages in a rollout so rife with confusion that even the new CDC director admitted she doesn't know exactly how many shots are in the pipeline. 

States were expected to find out their latest weekly allocation of vaccines on Tuesday amid complaints from governors and top health officials about inadequate supplies and the need for earlier and more reliable estimates of how much is on the way so that they can plan accordingly.

President Joe Biden suggested Monday  that he hopes the country can soon ramp up to 1.5 million shots dispensed per day. His administration has also promised more openness and said it will hold news briefings three times a week about the outbreak that has killed over 420,000 Americans.

Amid the rising frustration, the White House planned to hold a call with governors Tuesday to discuss the vaccine supply.

The setup inherited from the Trump administration has been marked by miscommunication and unexplained bottlenecks, with shortages reported in some places even as vaccine doses remain on the shelf.

Dr. Rochelle Walensky, Biden's brand-new director of the Centers for Disease Control and Prevention, was herself flummoxed over the weekend in trying to describe current supplies. 

"I can't tell you how much vaccine we have," she told "Fox News Sunday," describing the problem as a challenge left by the outgoing Trump administration. "And if I can't tell it to you, then I can't tell it to the governors, and I can't tell it to the state health officials. If they don't know how much vaccine they're getting, not just this week, but next week and the week after, they can't plan."

On Monday, Florida Gov. Ron DeSantis said the state can't meet growing demand from residents partly because an increase in vaccine promised by the government hasn't happened.

"We are at the mercy of what the federal government sends us, and right now we are able to go through it quicker than what we are receiving," he said.

White House press secretary Jen Psaki responded by saying that Florida has administered only about half of the vaccines it has been given. 

Georgia Gov. Brian Kemp said Tuesday that he doesn't expect the state's allotment of vaccines to increase in the coming weeks, which will limit progress in vaccinating those now eligible, including people over 65 and first responders. Rhode Island officials, meanwhile, said late last week that they can't even expand eligibility to those over 65 at current allocations from the government, despite complaints from advocates for the elderly. 

As of Tuesday morning, the CDC reported that just over half of the 41 million doses distributed to states have been put in people's arms. That is well short the hundreds of millions of doses that experts say will need to be administered to achieve herd immunity and conquer the outbreak.

The U.S. ranks fifth in the world in the number of doses administered relative to the country's population, behind No. 1 Israel, United Arab Emirates, Britain and Bahrain, according to the University of Oxford.

The reason more of the available shots in the U.S. haven't been dispensed isn't entirely clear. Some state officials have complained of a lag between when they report their numbers to the government and when the figures are posted on the CDC website.

And while some vaccination sites have canceled appointments for first-dose shots, many are believed to be holding large quantities of vaccine in reserve to make sure people who have already gotten their first shot receive the required second one on schedule, three to four weeks later.

In the New Orleans area, Ochsner Health said Monday that the number of vaccines it receives has declined, resulting in the cancellation last week of 21,400 first-dose appointments. Hospital officials said second-dose appointments aren't affected. 

Inova Health System, the largest health provider in Virginia's Washington, D.C., suburbs, said it is canceling all first-dose appointments at its mass vaccination clinics beginning Thursday because of inadequate supplies. Those who have already received a first dose will have their appointments for a second dose honored, it said. Inova has administered more than 70,000 shots.

In North Carolina, Greensboro-based Cone Health announced it is canceling first-dose appointments for 10,000 people and moving them to a waiting list because of supply problems. Also, UNC Health said Monday that the 10,000 doses it will receive this week are less than half of what it expected. 

Jesse Williams, 81, of Reidsville, North Carolina, said his vaccination appointment scheduled for Thursday with Cone Health was canceled, and he is waiting to hear when it might be rescheduled. The former volunteer firefighter said he misses attending church, playing golf and seeing friends in person, and he had hoped the vaccine would make more of those activities possible again. 

"It's just a frustration that we were expecting to be having our shots and being a little more resilient to COVID-19," he said.

The vaccine rollout across the 27-nation European Union has also run into roadblocks and has likewise been criticized as too slow. Pfizer is delaying deliveries while it upgrades its plant in Belgium to increase capacity. And AstraZeneca disclosed that its initial shipment will be smaller than expected.

The EU, with 450 million citizens, is demanding that the pharmaceutical companies meet their commitments on schedule.