Ronaldo completed a full training session on Monday for the first time since injuring his hamstring against Villarreal on April 20 and is expected to start the semi-final second leg against City who were held to a 0-0 home draw in the first game.
Benzema, who is also nursing a hamstring problem, could only do running exercises on Monday.
The 10-times European champions scraped a 1-0 win at Real Sociedad in La Liga on Saturday without their two top scorers.
Portugal marksman Ronaldo took no part in last week's tie in Manchester while France forward Benzema went off at halftime. Although Real had the better chances they were noticeably lightweight up front in the second period.
The club's all-time leading scorer Ronaldo has 47 goals in all competitions this season.
His hat-trick in the quarter-final second leg against VfL Wolfsburg overturned a two-goal deficit from the first match, averting an embarrassing exit for Zinedine Zidane's side.
City coach Manuel Pellegrini made eight changes to his team against Southampton on Sunday, in preparation for the trip to Madrid, but the plan backfired as they lost 4-2.
The Chilean was unapologetic about resting some of his players as his side look to reach a first Champions League final.
“I would do exactly the same again because we have an important game on Wednesday,” said Pellegrini.
Real are eyeing their 14th final appearance, 60 years after defeating Stade de Reims 4-3 to win the inaugural competition.
The Madrid heavyweights have progressed in seven out of eight European ties after being held to a goalless draw in the first leg, losing only to Spartak Moscow in the 1991 European Cup quarter-finals.
Real are also unbeaten in their last four Champions League matches at the Bernabeu against English opposition.
“Home advantage will help. The fans have to support us, we're counting on them and I'm sure they won't let us down,” said midfield anchorman Casemiro.
“When they get behind us they help a lot. Manchester City have to feel that the Bernabeu is strong.” – Reuters
Original source: Real banking on Ronaldo