United were missing the injured Rio Ferdinand, Wayne Rooney and Patrice Evra but were boosted by Tevez and Jonny Evans both passing late fitness tests.
In the opening exchanges United dominated possession, while Bolton relied on set-pieces and long balls to trouble the visitors but found Nemanja Vidic and Evans in fine form.
Bolton started with new loan signing Ariza Makukula up front and his physical presence troubled United in the air.
Phelan pleased to seal late win
Fabrice Muamba also provided muscle in midfield and he saw a long-range effort tipped over the bar by Edwin Van der Sar.
It took until the 35th minute for the first real chance of the game when Ronaldo's header was beaten out by Jaaskelainen.
The Bolton keeper was called into action twice again before half-time, first superbly stopping Ronaldo's fierce, low 20-yard free-kick and then routinely keeping out Anderson's long-range effort.
If Ronaldo troubled Bolton with his free-kicks, he was less assured with his final pass, while Tevez struggled to hold on to the ball up front.
Anderson and Michael Carrick were also erratic with their distribution and in truth United lacked the guile that Rooney, who was missing with a hamstring injury, provides.
Ronaldo again went close with a free-kick while Bolton offered very little, seemingly content to settle for a vital point.
Megson pleased with Bolton work-rate
With 17 minutes remaining Ferguson called for the cavalry and Ryan Giggs, making his 550th league appearance, and Paul Scholes entered the fray.
The veteran duo sparked United into life as they went in search of the vital goal.
Tevez went close with a header while Ronaldo also saw another powerful free-kick kept out by Jaaskelainen.
However, Kevin Davies almost shocked United.
Having earlier looped a header onto the roof of the net he later found himself unmarked inside United's six-yard box only to head over Van der Sar's goal.
But just as it looked as if the game would end goalless, Tevez escaped the attention of two defenders before crossing for Berbatov, six yards out, to head powerfully past Jaaskelainen to win the game for United.
Bolton manager Gary Megson: "Our part in that goal was particularly poor.
"I put three centre-halves in there at the end because we were out on our feet. It looked as though we would get something but it hasn't happened.
"I don't know if this result was ominous for the rest of the league but if anyone finishes above United, they will win it.
"They usually come good in the second half of the season but if you look at what Chelsea have done, they will be equally delighted. That is what good teams do."
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