Americans vaccinated against COVID-19 no longer need to mask up outdoors when there is no crowd, President Joe Biden said Tuesday, before celebrating by taking his first short walk at the White House without the face covering.

Biden told the nation in televised remarks from the leafy North Lawn that "stunning progress" has been made in getting vaccines administered and that stringent mask recommendations can now be relaxed.

"For those who haven't gotten their vaccination yet, especially if you're younger, or thinking you don't need it, this is another great reason to go get vaccinated. Now. Now," Biden said.

He was speaking shortly after the Centers for Disease Control, the top government health agency, notified fully vaccinated Americans that they can go mask-free most of the time outdoors.

"If you are fully vaccinated, you can start doing many things that you had stopped doing because of the pandemic," the CDC said in a statement.

Masks are still considered necessary for vaccinated people if they are at concerts, parades or large sporting events, even when outdoors, the CDC said.

Indoor activities also remain under a masks recommendation. This includes movie theaters and even "uncrowded" indoor shopping centers and museums, the CDC said.

More than half of all US adults have now received at least one of two vaccine doses. The surging rate of people seeking out vaccines has begun to taper, but new Covid-19 cases are also falling.

Biden said the change signified a shift in the way people can enjoy life as the summer approaches.

"Beginning today, gathering with a group of friends in a park, going for a picnic -- as long as you are vaccinated and outdoors, you can do it without a mask," he said.

Although he walked out of the White House to his podium on the lawn wearing a black mask, he walked back without.

"By watching me take it off and not put it back on till I get inside," he said when asked by reporters what message he was sending with his own mask wearing.

- Aid for India -

The CDC stressed that its newly relaxed guidance only applies to people who have had their full vaccine doses and are two weeks past the final shot.

Meanwhile, the US government announced it would send up to 60 million doses of the AstraZeneca vaccine abroad, after critics had accused Washington of "hoarding" the British-developed vaccine, which is not authorized in the country and will likely not be required to vaccinate Americans.

Biden told journalists that he is looking especially at helping India, which is in the grip of a deadly coronavirus surge.

Biden said he'd talked "at length" with Prime Minister Narendra Modi and "we are sending immediately a whole series of help that he needs, including providing for those Remdesivir and other drugs that are able to deal with this."

Biden said he has "hope and expectation" that assistance will extend to sending vaccines. That "will be my intention," he said.