WASHINGTON - The U.S. government Wednesday outlined extensive plans to provide Americans with free vaccinations against the coronavirus, but officials offered conflicting views on just how soon the preventative shots will be widely available.

Paul Mango, an official at the Department of Health and Human Services, told Bloomberg News that health experts expect the Food and Drug Administration will approve a safe vaccine by the end of 2020 and that the national government has contracts with drug manufacturers to produce enough doses so that all Americans can be vaccinated by the end of March.

Robert Redfield, the director of the Centers for Disease Control and Prevention, did not commit to a timetable during testimony at a Senate coronavirus hearing.

Asked for a vaccine timetable, Redfield said, "If you're asking me when is it going to be available to the American public, I think we're probably looking at late second quarter, third quarter 2021."

Another key coronavirus official, Army Lieutenant General Paul Ostrowski, said that as soon as the FDA approves the safety of the shots, "We will have vaccines moving to administration sites, within 24 hours."

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The CDC has told public health officials in all 50 states and U.S. territories to have plans ready to distribute a vaccine to health care workers and other high-priority groups, such as older people and those with underlying health problems, as early as Nov. 1.

That date is two days before the national election, when Republican President Donald Trump faces former Democratic Vice President Joe Biden for a four-year term in the White House. Trump has pushed federal officials to complete tests on possible vaccines as fast as possible.

U.S. polls show the rapid tests of would-be vaccines on thousands of volunteers that are being conducted in several countries have left many Americans skeptical of whether any approved preventative will be safe.

In one Associated Press poll, one in five Americans said they would not get a coronavirus vaccine, and 31% said they were unsure whether they would. Of those who said they would not get vaccinated, the overwhelming majority said they were worried about safety.

Health officials say that to protect the United States from the coronavirus, upwards of 70% either need to be vaccinated or have antibodies against the disease.

Health and Human Services Secretary Alex Azar said in a statement Wednesday, "We are working closely with our state and local public health partners...to ensure that Americans can receive the vaccine as soon as possible and vaccinate with confidence. Americans should know that the vaccine development process is being driven completely by science and the data."

Mango said, "For the overwhelming majority of Americans, no federal official will touch a dose of vaccine before it's injected into Americans." He said officials are working to ensure that "no American has to pay a single dime out of pocket to get a vaccine, and we're getting very close to that aspiration right now."

Until a vaccine becomes a reality, the U.S. health experts warned that Americans should continue to take precautions against the spread of the coronavirus.

Redfield, displaying a face mask, said, "These face masks are the important, powerful public health tool we have...I might even go so far as to say that this face mask is more guaranteed to protect me against COVID than when I take a COVID vaccine." COVID-19 is the disease caused by the coronavirus.

Admiral Brett Giroir, a key government coronavirus expert, told the Senate hearing that recent improvements in U.S. COVID numbers, such as a diminished daily death toll, "could be fleeting, or even reversed" if Americans don't take personal responsibility - "especially wearing masks and avoiding crowds."

An estimated 196,000 Americans have died from the coronavirus with another 6.6 million infected, according to the Johns Hopkins University, which is tracking cases around the world. Both figures are the highest for any nation.

The government described its vaccination plan as "much larger in scope and complexity than seasonal influenza or other previous outbreak-related vaccination responses."

For most vaccines, people will need two doses, administered 21 to 28 days apart, and both will have to come from the same drug manufacturer.