Ecclestone, in Dubai to announce a new sponsorship deal with Emirates airlines, said it was impossible to add another race "at this late stage."
There was speculation a European race would replace the Grand Prix of America.
The leading contender to fill the spot was Istanbul, which was dropped from the F1 calendar in 2012 after a disagreement with Ecclestone over the fee charged to stage the race. Portugal has also been mentioned in recent months as another candidate.
"Disappointed it didn't happen before," he said of the 20th race. "You can't suddenly slot it in."
Ecclestone also said he was "100 percent" confident that the Bahrain Grand Prix would go ahead despite ongoing unrest in the Gulf nation, adding that he "hoped things were a little more peaceful" this year.
The Bahrain Grand Prix was run without incident this year, although it was a public relations disaster for F1. Sectarian violence rocked the streets of Manama causing death and injury during the race weekend, and created a disturbing background for the race which was won by Red Bull's Sebastian Vettel.
"I haven't seen the kind of troubles we experienced at this time last year," Ecclestone said.
The F1 boss also ruled out bringing a 12th team onto the grid in 2013, putting to rest talk that a group of Canadian and American investors would have a team to replace HRT, which can't afford to compete this year.
As for another Persian Gulf race in Dubai or Qatar, Ecclestone said it would be "difficult to pop another one in there" given F1 is limited to 20 races.
Ecclestone said he was confident there would be 20 races in 2014, confirming that Russia will stage its first F1 race in Sochi. After visiting Sochi this week, Ecclestone said "everything seems to be good" in terms of preparations. Sochi will also host the 2014 Winter Olympics.
"He (President Vladimir Putin) seems delighted with the Olympics and Formula One," Ecclestone said. "It was good. I was very impressed with what they have done."