On the debate stage on Thursday night, President Donald Trump went further than he has ever gone in predicting the development of a COVID-19 vaccine, declaring that “it’s ready” and “it’s going to be announced within weeks.”

His assessment counters the consistent message from the president’s own public health officials, such as Dr. Anthony Fauci, who has said a COVID-19 vaccine is unlikely to be widely available until 2021, and that masks and social distancing measures are likely to be in place until later that year.

Pressed on that by the debate moderator, NBC’s Kristen Welker, Trump said, “my timeline's going to be more accurate.” And asked whether he was offering a guarantee, Trump said he wasn’t—“but it will be by the end of the year.”

“It's going to be announced within weeks. And it's going to be delivered,” said Trump. “We have Operation Warp Speed, which is, the military is going to distribute the vaccine.”

This is hardly the first time that Trump has offered a bullish vision of the vaccine development process, saying at various points all year that one would arrive within an unprecedented timeframe. He has especially emphasized that it would come before the 2020 election. Democrats, meanwhile, have expressed concern that the Trump administration might rush a vaccine for political reasons, or announce one shortly before the election for political gain.

Joe Biden, the Democratic presidential nominee, responded to Trump by noting the president’s record of rosy predictions about the pandemic that haven’t borne out, and said there is “no prospect” that there will be a vaccine for most Americans before mid-2021.

“This is the same fellow who told you this is going to end by Easter last time,” said Biden, referring to Trump’s early insistence that the virus would simply go away and wanted to see Church pews full by Easter. “This is the same fellow who told you that don't worry, we're going to end this by the summer. We're about to go into a dark winter. A dark winter.”

Trump, despite his penchant for putting the pandemic in the best possible light, made another admission on Thursday: He said he took “full responsibility” for how he has handled COVID-19. But he immediately backtracked on that, too. “It’s not my fault that it came here,” said Trump, immediately after accepting responsibility. “It’s China’s fault.”