Ecclestone, the F1 chief executive, opened up the twentieth slot to a potential new European venue, but he said on Tuesday that he could not now fill it "at this late stage".
"(I'm) disappointed it (the 20th race) didn't happen," he said in Dubai on Tuesday, where he announced the airline Emirates as a major new F1 sponsor.
"(But) you can't suddenly slot it in."
However, the 82-year-old Briton was quoted by the Gulf News as saying 20 is the ideal number for future F1 calendars.
"Twenty races is more or less what we should aim for in a season," he said.
Ecclestone said he was adamant Bahrain would host its grand prix as scheduled this year, because things seem "a little more peaceful" in the Kingdom in 2013.
Finally, he definitively dashed the hopes of a group of Canadian and American investors, who had hoped to buy up defunct HRT's assets and race this season.