President Trump on Friday unveiled the team leading a federal effort that he hopes will produce a coronavirus vaccine by the end of the year, an accelerated timeline that has been met with skepticism from health experts.

“When I say quickly, we’re looking to get it by the end of the year if we can, maybe before,” Trump said in remarks from the White House Rose Garden, officially laying out the objectives of “Operation Warp Speed,” a public-private partnership to accelerate the development of a vaccine for the novel coronavirus.

Trump described the project as “a massive scientific industrial and logistical endeavor unlike anything our country has seen since the Manhattan Project.” He said the project would begin to manufacture vaccines as they go through trials so that a proven vaccine would be ready to distribute once trials are completed.

“We’re gearing up,” the president said. “It’s risky, it's expensive, but we’ll be saving massive amounts of time.”

Pressed later on the timeline, Trump appeared to extend it slightly, saying “we hope to be able to do something by the end of the year or shortly thereafter.”

Trump has tapped Moncef Slaoui, a former pharmaceutical executive, as the project’s chief scientist and Army Gen. Gustave Perna as the project’s chief operation officer. Their appointments were first reported earlier this week.

The president said the administration was working to narrow down a group of potential vaccines from a set of 14 being developed to inoculate individuals against the coronavirus, which has infected more than 1.4 million Americans and led to more than 85,000 domestic deaths. The administration would then work with the private sector to manufacture those chosen vaccines as they are tested for safety and effectiveness.

Health and Human Services Secretary Alex Azar later said the goal was to have a vaccine developed and available to the general public by January, noting that the administration would employ emergency use authorization and other tools to make the vaccine available.

Slaoui acknowledged in his own brief remarks Friday the high bar of meeting the administration’s goals, but expressed confidence that the public-private effort would deliver “a few hundred million doses of the vaccine by the end of 2020.” Perna described the effort as a “herculean task.”

Trump first predicted earlier this month that the United States would have a vaccine developed by the end of the year, a prospect that health experts say is unrealistic.

“I think we’re going to have a vaccine by the end of the year, and I think distribution will take place almost simultaneously because we’ve geared up the military,” Trump told reporters Thursday before leaving for a trip to a Pennsylvania medical equipment distributor.

Appearing on Fox Business earlier Friday, Azar said the administration hoped to have “hundreds of millions of doses” of one or more safe vaccines by the end of the year but acknowledged the goal was a “stretch.”

Anthony Fauci, a member of the White House's coronavirus task force who was present at Friday’s event but did not deliver remarks, has said it’s possible a vaccine will be ready in January. Fauci initially expected it to take between 12 and 18 months to produce a vaccine when work began this past January, which put the earliest date at the start of next year.

Fauci also cautioned during testimony before a Senate panel on Tuesday that there was “no guarantee” a given vaccine would actually be effective, though he expressed optimism that the administration would find a viable option.

“Given the way the body responds to viruses of this type, I'm cautiously optimistic that we will, with one of the candidates, get an efficacy signal,” Fauci said.

Meanwhile, Rick Bright, an ousted federal vaccine doctor-turned-whistleblower, said Thursday that he believed it would take longer than 18 months to develop a vaccine.

“There is a lot of optimism. There is a lot of hope," Bright told a House committee. “But that doesn't make a vaccine. There's a lot of work that needs to be done to make a vaccine.”

Anand Parekh, chief medical adviser at the Bipartisan Policy Group, told The Hill that the more likely scenario would be a vaccine being available to the general public in fall 2021, even with the accelerated program. Parekh said the initial vaccine is likely to be prioritized to health care workers and more vulnerable populations, like the elderly.

“Even if some folks in early 2021 got the vaccine, we’re not talking about the entire American public,” Parekh said.

There are currently more than 100 potential COVID-19 vaccines being developed around the world, several of which are in clinical trials.

Various states have begun to loosen restrictions meant to curb the spread of the virus as they look to allow Americans to gradually return to work and some semblance of normal life.

Still, health experts say that Americans will need to continue to implement some degree of social distancing practices until a vaccine is developed in order to prevent future outbreaks of the virus even as cases subside across the country. The administration has also been under pressure to ramp up testing and contact tracing capabilities, which are viewed by experts as crucial elements to containing the virus as states reopen.

“We’re going to be in this period where we’re going to be lifting and reinstituting a variety of interventions,” said Parekh, a former HHS deputy assistant secretary. “This is going to be part of our reality for all while.”

Trump has tried to project optimism about the path forward in confronting the virus, declaring the U.S. past the worst point and putting increasing focus on reopening the economy, which has been devastated by coronavirus-related business closures. But the president’s statements have at times been in conflict with statements made by health experts.

Trump during an exchange with a reporter at Friday’s event suggested the virus would go away even without a vaccine.

“It's not solely vaccine-based. Other things have never had a vaccine and they go away,” Trump said. “So I don't want people to think that this is all dependent on a vaccine, but a vaccine would be a tremendous thing.”

Fauci has repeatedly said the virus will not disappear because of its transmissibility.

Updated: 5:07 p.m.