U.S. pharmaceutical giant Pfizer Inc. said Friday that its application for emergency use authorization in the United States for its potential coronavirus vaccine will take place no earlier than the third week of November.

The announcement may be a disappointment to President Donald Trump, who has been raising expectations that vaccines could be ready around the time of the Nov. 3 presidential election in an apparent bid to boost his faltering electoral prospects.

A pedestrian wearing a protective mask walks past Pfizer Inc. headquarters on July 22, 2020 in New York City.(Getty/Kyodo)

Pfizer is one among several companies in the midst of final-stage clinical trials for potential coronavirus vaccines in the country.

In an open letter posted on the company's website, Chairman and CEO Albert Bourla said that if data from trials support the move, Pfizer will apply for emergency use authorization in the United States "soon after the safety milestone is achieved in the third week of November."

Bourla said the company may find later this month whether or not its vaccine is effective, meaning it can help prevent COVID-19 disease in at least a majority of vaccinated patients.

In addition, the company has to prove that the vaccine is safe and the U.S. Food and Drug Administration requires that companies provide two months of safety data on half of the trial participants following the final dose of the vaccine, according to Pfizer.

"Based on our current trial enrollment and dosing pace, we estimate we will reach this milestone in the third week of November," he said, noting, "We are operating at the speed of science."

Pfizer, which is developing the vaccine with German partner BioNTech SE, has agreed with the Japanese government to supply the country with 120 million doses of a vaccine for 60 million people if the development efforts are successful.

Another U.S. firm Moderna Inc. has also reportedly said it will not be ready to seek emergency use authorization from the FDA before Nov. 25 at the earliest.