The Food and Drug Administration (FDA) experts backed the move on Tuesday, paving the way for emergency authorisation within a matter of weeks.
In September, the company said its trial data showed the Covid jab was safe for children in that age group.
The US is already giving the vaccine to those aged 12 and over.
This latest decision affects some 28 million US children.
The decision now awaits further approval from the FDA and the Centers for Disease Control and Prevention (CDC). They are expected to do that on 2 November, meaning vaccinations could begin the very next day.
The FDA's expert panel determined that the benefits of having the jab outweigh any other health risks.
Company trial data submitted to regulators in September said the jabs produced a "robust" antibody immune response in that age bracket.
Children aged five to 11 are given a jab with a third of the dosage given to adults.
Regulators, however, also had to weigh up the risk of heart inflammation, a very rare side-effect of the Pfizer and Moderna vaccines.