Alonso is now 60 points behind with six races remaining, but Domenicali is refusing to give up hope.
He cited Mark Webber's last-lap retirement from the Singapore Grand Prix as proof that opportunities could arise provided Alonso continues to be Vettel's nearest challenger.
"The only thing we can try and do is to stay there in second and if there is an opportunity, we will take it," said Domenicali.
"Without a problem for Vettel it's very difficult to fight for the championship, but you never know.
"What happened to Mark on the last lap can happen to Sebastian and if it happens one or two times, we are there.
"Never say never. It's very difficult but we will try."
We rate the drivers after the Singapore GP
Domenicali accepts Red Bull has a stronger car than Ferrari, but stressed that the team is still working to get more performance out of the current F138.
"At this stage, it is clear that Vettel and Red Bull have a better package but we will try to deliver on track what is still in the pipeline," he said.
"At home, we are 99 per cent dedicated to the 2014 car because it is a huge and complex project that it is very important to be on top of so we need to fight with what we have.
"Congratulations to Red Bull because they are doing an incredible job, but we are still improving after a very difficult July.
"If we hadn't lost some points at the beginning of the season, the situation in the championship would be different."
Domenicali believes that there is little Ferrari can do to make major strides forward in terms of tyre management.
Alonso suggested after the Singapore Grand Prix that the change of Pirelli rubber in Hungary, with the 2013 compounds mated to last year's construction, was the moment when he said "bye bye" to the championship.
"It is a fact that the change in specification reshuffled the general performance of all the cars," said Domenicali.
"The performance that we had at the beginning is not there anymore.
"We will try [to work on that] but it's micro-management. There is nothing huge that it is possible to do."