Ecclestone told Forbes at Silverstone that he said to FIA president Jean Todt: "'You must see how honest they (Haas) are. Tell Haas to put a deposit down' and apparently they have."
US-based Haas, a Nascar team co-owner who for the F1 project is already aligned with Ferrari, intends to make its debut in 2016, probably with at least one American at the wheel.
The identity of that American could be Californian Alexander Rossi, who has now left Caterham as a F1 test and GP2 driver.
"We have a great opportunity to grow the sport in the States," he said on Wednesday, "and I believe the timing is perfect.
"I'm also very pleased to see an American F1 entry, Haas Formula, with plans to join the F1 grid in 2016," Rossi added.