Inter beat Bologna 3-0 at the San Siro and second-placed Roma remained a point behind with six games to go thanks to a 1-0 win at Bari.
AC Milan, three points off the pace in third, triumphed 3-2 at Cagliari to end a three-game winless streak.
"We have to keep trying to win match after match," Ranieri told Sky television after his side extended their unbeaten league run to 22 games.
"We won't have any dips (in form) although there may be a match that goes badly. We are in good shape physically."
Some pundits view Roma as favourites because Inter are also competing for glory in the Champions League. Jose Mourinho's team take a 1-0 lead into Tuesday's quarter-final second leg at CSKA Moscow.
Ranieri, however, said Inter were good enough to challenge for both trophies.
"While Inter are in front it's in their hands," he said. "They have a superb squad and can fight on all fronts."
Mourinho declined to speak to reporters again on Saturday, continuing a month-long media boycott before and after Serie A matches.
Inter's Esteban Cambiasso said the champions were confident of bagging a fifth consecutive title despite shaky domestic form of late.
"We are first in the standings and a point in front," the Argentine midfielder said. "We know it'll be hard but if we win our games we'll be Italian champions."
