Once considered the hot favourite to return with his former team Force India this year, the long delay has caused some commentators to assume that German Sutil, 30, is now less likely to race.
But Sutil's manager Manfred Zimmermann insisted: "Basically, we still believe in the 2013 comeback."
He also admitted to DPA news agency, however, that he is "not sure" if Sutil will have a cockpit to occupy for the forthcoming opening 2013 test at Jerez.
"At the moment we are waiting for the final decision, and of course we would prefer it sooner rather than later," Zimmermann said.
As for whether Timo Glock's shock departure at Marussia had contributed to the delay, Sutil's manager said the events are "unrelated", whilst acknowledging that the pay-driver situation was "significant for F1".