Biden touts vaccines as US injections slow

US President Joe Biden has urged more Americans to take advantage of COVID-19 vaccinations as the rate of inoculations slows despite a nationwide effort to get shots in arms to stop the spread of the coronavirus.

"The data couldn't be clearer. If you're vaccinated, you're safe," Biden on Thursday told a Raleigh, North Carolina crowd that planned to visit neighbourhoods to advocate for getting the vaccine.

"You are still at risk of getting seriously ill or dying if you in fact have not been vaccinated."

Only 55 per cent of the southern state's adult population has had at least one shot despite a slew of incentives, including a $US1 million ($A1.3 million) lottery, according to the North Carolina Department of Health and Human Services.

The White House acknowledged this week that it would not meet a self-imposed deadline to get 70 per cent of US adults at least partially vaccinated by July 4, noting that those aged 18 to 26 have been especially reluctant to get the shots.

Biden's visit came as the more contagious Delta variant of the virus is taking hold across the globe and emerging as the biggest obstacle to stopping COVID-19 within US borders, infectious disease expert Anthony Fauci said earlier this week.

"Unvaccinated people are incredibly vulnerable," Biden said, referencing the Delta variant.

Sixteen states and the District of Columbia have reached Biden's vaccination goal, but the country as a whole and several other states continue to lag.