The introduction of a second American Formula 1 race in Miami could well spell danger to the current United States GP in Austin, according to organiser Bobby Epstein.

His event at the Circuit of the Americas has been seen as a big positive for the revival of the sport in the country since it began in 2012, however, despite the growing popularity it hasn't stopped the trend of falling attendances in recent years.

Now faced with the possibility of a rival race in Florida, Epstein admits in the first few years at least, the likelihood of splitting the fanbase between the two could actually work against the vision of F1 owners Liberty Media.

"I think in the long term it can be good but there is a risk," he told Motorsport.com. "There is clearly a risk to diluting the product before the fan base has increased.

"But when the long-term goal is to increase the fan base, it is a chicken or egg scenario. Which comes first? In the early years, it remains to be seen if that is a positive for us.

"The first year, you haven’t increased the fan base but you’ve increased the options, so it will be tough at first. We will see how it impacts us."

The key, the Austin promoter believes, is the effectiveness and quickness of promotion to attracting Americans to F1.

"There are hundreds of millions of people in North American so my mindset is to be optimistic," he explained.

"I’m certainly a little apprehensive, but very optimistic that it is a race against time as to whether or not you can build the fan base before the pain of splitting up the fans takes its toll.

"We want it to happen and we want it to happen fast. And I think we share that with Liberty."

Many questions still hang over the proposed race in Miami, however, with an initial layout having to be redrawn after opposition and further unhappiness by residents in the other areas threatens to derail the proposal.

A deadline this week for a deal with Liberty has come and past without any progress and Andres Althabe, president of the Biscayne Neighborhoods Association, has laid out what would be required to get their approval.

"We are now waiting for the contract that the City Manager will present to the City Commission, but if we don't have a clear understanding of the benefits that the race will bring to the City of Miami, we will consider opposing the City Commission approving the contract," he told Forbes.