The Austrian race takes place on 22 June, two weeks before the British Grand Prix on 6 July.
The New Jersey race has been beset by financial and logistical problems since it was initially proposed in 2012 and there must now be severe doubts as to whether it will ever take place.
But the New Jersey race organiser Leo Hindery said he was still pressing ahead with plans for the race and Ecclestone said in a statement he had "no doubt" it would happen in 2015.
Hindery said: "Bringing a world-class race to the world's largest media market is a huge undertaking that has required balancing construction of our road course, without tapping any public money, with the sport's own timing demands."
Mexico's race had to be postponed after it became clear organisers did not have enough time to refurbish the track in Mexico City before next year's planned November date.
The Autodromo Hermanos Rodriguez last hosted a grand prix in 1992 and needs extensive remodelling before being suitable for modern F1.
The absence of the Korean Grand Prix ends an ill-starred four-year spell in F1 for the track built near Mokpo in the country's far south-west.
The local government had planned to build a new city around the Korean International Circuit, but ran out of money and have consistently been asking for the sanctioning fee to be reduced.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.