WASHINGTON — President Joe Biden on Tuesday set a new vaccination goal to deliver at least one dose to 70% of adult Americans by July Fourth, focusing on easing access to shots as his administration tackles the vexing problem of winning over those reluctant to get inoculated.

The new goal comes as demand for vaccines has dropped off markedly nationwide, with some states leaving more than half their vaccine doses unordered. Biden called for states to make vaccines available on a walk-in basis and will direct many pharmacies to do the same, and his administration is for the first time moving to shift doses from states with weaker demand to areas with stronger interest in the shots.

“You do need to get vaccinated,” Biden said from the White House. “Even if your chance of getting seriously ill is low, why take the risk? It could save your life or the lives of somebody you love.”

Biden’s goal, which includes delivering at least the first shot to 181 million adults and fully vaccinating 160 million, is a tacit acknowledgment of the declining interest in shots. Already more than 56% of adult Americans have received at least one dose of a COVID-19 vaccine and nearly 105 million are fully vaccinated. The U.S. is currently administering first doses at a rate of about 965,000 per day — half the rate of three weeks ago, but almost twice as fast as needed to meet Biden’s target.

“I’d like to get it 100%, but I think realistically we can get to that place between now and July Fourth,” Biden said.

He said the administration would focus on three areas as it tries to ramp up the pace of vaccinations: adults who need more convincing to take the vaccine, those who have struggled to obtain a shot and, once the FDA gives approval, adolescents ages 12 to 15. Acknowledging that “the pace of vaccination is slowing,” Biden acknowledged that the inoculation effort was “going to be harder” when it comes to convincing “doubters” of the need to get the shot.

He said the most effective argument to those people would be to protect those they love. “This is your choice: It’s life and death.”

Biden’s push comes as his administration has shifted away from setting a target for the U.S. to reach “herd immunity,” instead focusing on delivering as many shots into arms as possible. Officials said Biden’s vaccination target would result in a significant reduction in COVID-19 cases heading into the summer.

To that end, the Biden administration is shifting the government’s focus toward expanding smaller and mobile vaccination clinics to deliver doses to harder-to-reach communities. It is also spending hundreds of millions of dollars to try to boost interest in vaccines through education campaigns and access to shots through community organizations that can help bring people to clinics.

Biden touted grocery stores giving discounts to shoppers who come to get vaccinated and said that getting the inoculations could be “easier and more fun” when sports leagues hold promotions to gets shots for their fans.

Ahead of the Food and Drug Administration’s expected authorization of the Pfizer vaccine for adolescents ages 12 to 15 by early next week, the White House is also developing plans to speed vaccinations to that age group. Biden urged states to administer at least one dose to those in that age group by July Fourth and work to deliver doses to pediatricians’ offices and other trusted locations, with the aim of getting as many of them fully vaccinated by the start of the next school year.

While younger people are at dramatically lower risk of serious complications from COVID-19, they have made up a larger share of new virus cases as a majority of U.S. adults have been at least partially vaccinated and as higher-risk activities like indoor dining and contact sports have resumed in most of the country. Officials hope that extending vaccinations to teens — who would be eligible to get the first dose in one location and the second elsewhere — will further accelerate the nation’s reduced virus caseload and allow schools to reopen with minimal disruptions this fall.

The urgency to expand the pool of those getting the shots is rooted in hopes of stamping out the development of new variants that could emerge from unchecked outbreaks and helping the country further reopen by the symbolic moment of Independence Day. Though White House officials privately acknowledge the steep challenge, Biden sounded an optimistic note.

“The light at the end of the tunnel is actually growing brighter and brighter,” Biden said.

Biden’s speech comes as the White House announced a shift away from a strict by-population allocation of vaccines. The administration says that when states decline the vaccine they have been allocated, that surplus will shift to states still awaiting doses to meet demand. Those states would have the shots available whenever demand for vaccines in their states increases.

Governors were informed of the change by the White House on Tuesday morning.