Top U.S. health officials urged Americans to get vaccinated against COVID-19 on Wednesday, saying U.S. regulators' pause on Johnson & Johnson shots, following reports it can cause blood clotting, should boost confidence in the vaccines' safety.

U.S. federal health agencies on Tuesday recommended pausing use of J&J's COVID-19 vaccine for at least a few days after six women under 50 developed rare blood clots after getting the shot.

White House COVID-19 response coordinator Jeff Zients said that U.S. regulators' quick response to the clotting reports should give Americans more confidence, not less, that any shots they receive will be safe.

"We believe that by empowering Americans with data and facts, we will strengthen the public's trust in government, and increased their confidence in the vaccines," said Zients at a press briefing on Wednesday.

Zients said the White House had taken action to speed up production and delivery schedules for Moderna Inc and Pfizer Inc vaccines in a bid to offset the pause in J&J dose shipments and maintain the pace of the United States' inoculation program.

He said J&J shots have so far made up less than 5% of the more than 190 million COVID-19 vaccine doses that have been administered in the United States as of Tuesday.

"People who have vaccine appointments to receive (Pfizer and Moderna) vaccines should keep their appointments, and we will work with our partners across the country to reschedule those who are intending to get the Johnson and Johnson vaccine," U.S. Centers of Disease Control and Prevention Director Dr. Rochelle Walensky said on Wednesday.

The United States vaccine rollout is accelerating, Zients said, with providers now administering around 3.3 million shots daily on average.