Washington DC - President Joe Biden said Tuesday he wants 70% of the US population to have had at least one coronavirus vaccine jab by July 4, when the country celebrates Independence Day.

By that date, he said, 160 million people should already be fully vaccinated.

"Now that we have the vaccine supply, we're focused on convincing even more Americans to show up and get the vaccine available to them," he said from the White House, vowing to make it "easier than ever."

So far, 56% of US adults have received at least one shot, according to data from the Centers for Disease Control and Prevention, with 105 million people considered fully vaccinated.

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To meet the new goal, nearly 100 million additional vaccinations would need to be given in the next 60 days, the White House said.

To help achieve this, the government will instruct pharmacies to allow vaccinations without prior appointments. About 40,000 pharmacies get their vaccine directly from the government.

The administration is also changing the formula used to distribute doses that had been in place since the vaccination campaign began in mid-December.

Previously, all states received deliveries in strict proportion to their population. In the future, states that already have more supply than demand will be able to call for only a portion of the doses they are entitled to. The surplus then goes back to the federal government and can be called up by states that need more vaccine.

At the height of the vaccination campaign in the US, more than 3 million people were being given jabs every day. Now the White House is trying to inject fresh momentum as that number trends downward.

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There are regional variations, too. For instance, only about a third of the population of the southern state of Mississippi has received at least one dose. In the north-eastern state of Massachusetts, on the other hand, nearly 60% received at least the first injection and demand remains strong.

Biden also noted that there will be a new push to reach people in rural areas who may find it inconvenient to get to vaccination sites.

Three vaccines are currently in use in the US: the two manufactured by Moderna and Pfizer/BioNTech, which are administered in two doses, as well as the single-shot Johnson & Johnson.