Speaking at Sunday's Bahrain Grand Prix, Ecclestone said he held talks with the sport's governing body and there was agreement about expansion next season.
"They will be accepted, and we've also accepted another team as well, although whether they'll make it or not is another story," Ecclestone said when asked about a possible Haas entry.
The other 2015 bidder is believed to be an Eastern Europe-based entry backed by Colin Kolles, who formerly was at defunct teams HRT, Midland and Spyker.
FIA President Jean Todt confirmed that applications were being considered and said a decision will be announced "in coming days." Those applying will need approval from the governing body and the commercial rights holder, headed by Ecclestone.
At the NASCAR race in Fort Worth, Texas, Haas said he had not heard from Ecclestone or the governing body.
"We haven't been notified by the FIA, but Bernie is kind of half Formula One, so I'm sure what he says goes," Haas said. "I have no doubt that even if Mr. Ecclestone says he's OK with it, there's probably another few weeks of legal paperwork" before FIA would issue a license.
The new entries may replace existing teams rather than add to the grid. Several F1 teams are struggling financially.
Haas is the founder of the Stewart-Haas NASCAR team based in North Carolina. He also operates one of the world's most sophisticated wind tunnels for the testing of car aerodynamics, which would aid any new F1 entry.
He's the owner of Haas Automation, which is one of the largest machine tool builders in the world. Haas said his company currently does $1 billion in annual sales, and he believes entering Formula One could help him double that number.
"It's not that we're trying to individually sell machines. We're trying to make people aware of Haas Automation as a company," he said.
He added: "We're just trying to bring our awareness up and Formula One is even more important because half our sales are outside the country. So we think Formula One would be a really great way of bringing us awareness and increasing our sales."
But Haas said he's running out of time to get a team ready for the 2015 season.
"We needed to know about two months ago," he said. "If Mr. Ecclestone says that we're accepted and the FIA issues us some kind of notice in the next few weeks, then we can entertain 2015. But if we lose another month, I don't think we could do it."
His team would be based in North Carolina, next to the existing NASCAR shop. A possible barrier to Haas' involvement in F1 could be a set of standards FIA applies to those involved at high levels of ownership and management. Haas has a conviction for tax evasion and related charges.
A U.S. team was initially admitted to F1 in 2010 but lacked the funding and development to join.
AP Auto Racing Writer Jenna Fryer contributed to this report from Fort Worth, Texas.