Ramos was forced out of the 4-0 victory in Belarus on Friday and did not train with the squad on Sunday.
The defender will be back for Monday's final training session before the match at Atletico Madrid's Calderon stadium, Del Bosque said.
"He told me he was better and we are confident he'll be available for tomorrow," Del Bosque said.
"But if he cannot play we will not force the issue, we won't take risks. In that case someone else will play."
Spain's defence would be considerably weakened without Ramos who, with Real Madrid team mate Raul Albiol, is one of only two recognised centre backs in the squad.
Barcelona pair Carles Puyol and Gerard Pique are out injured and Del Bosque started with converted midfielder Sergio Busquets alongside Ramos against Belarus as Albiol has hardly featured for Real in recent months.
Spain top Group I on goal difference after both teams won their opening two matches, the world and European champions beating Georgia and Belarus and France dispatching Belarus and Finland.
Tuesday's match could go a long way in deciding who qualifies for the 2014 finals in Brazil as winners of the five-nation group and avoids the play-offs.
While Del Bosque waits on Ramos, he has decisions to make at the other end of Spain's formation, with record scorer David Villa itching for more playing time as he continues his recovery from a broken leg.
Villa came on for the last quarter of an hour of the Belarus game and was denied a goal by the crossbar.
"I need to be patient but I am ready to play already," he said at a book presentation at Spain's training camp outside Madrid on Monday.
"I know my leg will respond, I am not so sure about my stamina," added 30-year-old Barcelona forward Villa.
"I found it really hard to smile these past months but my friends and family helped me through it and I will thank them for the rest of my life. Now I am happy and I smile more."