President Joe Biden on Wednesday hailed his government's "stunning" achievement in administering 200 million Covid-19 vaccine shots across the United States ahead of schedule.

Biden said the landmark had been reached a week before he hits his administration's 100-day mark -- the deadline he'd announced for meeting the 200 million doses challenge.

"Today we did it, today we hit 200 million shots," he said in a televised speech from the White House. This is "an incredible achievement for the nation." Biden called the 200 million shots in 100 days a "goal unmatched in the world or in prior mass vaccination efforts in American history."

"The progress we've made has been stunning," he said. Announcing a tax break to encourage businesses to give all employees a day off for vaccinations, Biden said the country was still "on track" to being able to celebrate the July 4th Independence Day holiday in relative normality.

But he warned that rising infection rates in parts of the country showed that it was too early to declare victory. "If we let up now and stop being vigilant, this virus will erase the progress," he said. While the United States leads the world in reported Covid-19 deaths, it has also raced ahead in the vaccination stakes, outperforming some major European countries and neighbouring Canada.

Biden came into office on January 20 initially vowing to get 100 million shots administered in his first 100 days. On March 25, with vaccination deliveries far ahead of their targets, he doubled the goal. Starting in May, all states will be required to lift restrictions on eligibility for access to the free shots. Many have already done that.

Dampening the celebratory mood in the White House is a surge of infection rates in parts of the country, including the state of Michigan. Death rates, however, remain down nationwide as a result of the high vaccination rate among the elderly and improved care.