The 33-year-old goalkeeper saw his side push the world and European champions all the way at Yankee Stadium in New York during the early hours of Wednesday morning before eventually slipping to a 2-0 friendly defeat.
Forde said: "I certainly think we will finish second for that qualifying spot and go to Rio."
While it was dogged defence and undying commitment rather than flowing football which frustrated the Spaniards for much of the contest, Forde has seen enough in recent months to believe Ireland can secure second place in Group C when they return to competitive action in the autumn.
Giovanni Trapattoni's men face Sweden, who beat the Faroe Islands 2-0 in Solna on Tuesday night, in Dublin on September 6 and then head for Austria four days later with all three sides currently on 11 points.
Forde said: "September is going to be huge. They are great games to be playing in, Sweden at home and Austria away, and they will probably be the deciders as well. I think we have sent out a few shockwaves to those nations. They know all about us now and that we are in with a good chance."
Forde's confidence is based on both the emergence of a new generation of players, spearheaded by Seamus Coleman and James McCarthy, and a run of results which has seen a drastic turnaround in fortunes since the Republic were trounced 6-1 by Germany at the Aviva Stadium in October.
The defeat by Spain was just their second in nine outings since, and few, including Trapattoni judging by his pre-match comments, expected them to maintain that run in the final leg of their quartet of summer fixtures.
Forde and his team-mates were disappointed, though, to have been beaten, despite a 4-0 thumping at the hands of the same opponents at the Euro 2012 finals almost a year ago to the day.
Circumstances had a part to play, with central defender Sean St Ledger having what he thought was an 81st-minute equaliser ruled out for offside after substitute Roberto Soldado had belatedly fired Spain ahead. Fellow newcomer Juan Mata doubled his side's lead at the death.
- Sports & Recreation
- Giovanni Trapattoni