Democratic New York City Mayor Bill de Blasio said Wednesday that more than 20,000 COVID-19 vaccination appointments were rescheduled this week due to a supply issue.

“We’ve had to tell 23,000 New Yorkers who had an appointment this week that they will not be able to get that appointment for lack of supply,” de Blasio said.

“We’ve got something right in front of us today,” de Blasio continued. “The fact that we’re going to have to cancel tens of thousands of appointments today for folks who need a first dose, that’s something we should avoid at all costs when we have 65,000 doses sitting on the shelf.” he said. (RELATED: New York City Establishes Day Of Remembrance For COVID-19 Victims)

The good news: Today we will hit half a million COVID-19 vaccinations in our city.
The bad news: We’re running low on doses.

We’ve had to reschedule thousands of appointments this week due to lack of supply. Let us use our second doses in reserve so we can keep saving lives. pic.twitter.com/0zFcjoXsPW

— Mayor Bill de Blasio (@NYCMayor) January 20, 2021

De Blasio said at a news conference that a delivery delay of Moderna’s vaccine contributed to the cancellations. City health commissioner David Chokshi said the rescheduled appointments were for people who would be receiving their first dose.

“We expect those vaccines are intact, they will be safe and effective, and we will get them for New York City over the course of today and tomorrow,” Chokshi said.

The supply disruption could hamper the mayor’s goal to vaccinate 1 million NYC residents by the end of January.

“The most important New Year’s resolution I could possibly offer you in the month of January 2021, we will vaccinate one million New Yorkers,” de Blasio said Dec. 31. “This city can do it. The amazing health care professionals of this city are ready.”

So far, 494, 596 vaccines have been administered in New York City, according to city health data.