Worcestershire 131 and 99 for 3 (Libby 51*) trail Durham 381 (Bedingham 121, Jones 78, Lees 52, Tongue 4-73) by 151 runs
David Bedingham propelled Durham into a position of strength with his third century of the season on day two of the LV=Insurance County Championship encounter with Worcestershire at New Road.
The competition's leading run-scorer hit a chanceless 121 to take his tally for the summer to 787 at an average of 71.54.
Bedingham and Michael Jones shared a fifth-wicket stand of 171 to help Durham to 381 all out and a first innings lead of 250.
Worcestershire rallied after a disappointing first session, in claiming six wickets for 76 to secure maximum batting points with Josh Tongue returning 4 for 73 from 25 overs.
But there is still sufficient encouragement in the pitch for the bowlers and Matty Potts picked up two wickets as Worcestershire limped to 99 for 3 by the close despite an unbeaten Jake Libby half-century.
"We said the first hour would be key and we played and missed a bit but you need a bit of luck in a big partnership," Bedingham said at the close. "We got through it, and the magic spray did the trick after I got hit in the ribs by Tongue, who bowled well the whole day."
It has been a feast-or-famine campaign for Bedingham who has scored three hundreds and two fifties but in eight other knocks in the Championship has a highest score of 33.
He was in fine fettle today as Durham built effectively on their overnight 140 for 4, greeting the introduction of Dillon Pennington into the attack with three boundaries in his first over and hitting legspinner Brett D'Oliveira for two straight sixes - the second of which completed an 84-ball fifty.
Jones went to a 116-ball half-century and Durham batted through the morning session without losing a wicket and adding 102 runs.
It was a different proposition for batting once the second new ball had been taken and Leach made the breakthrough when Jones edged through to keeper Ben Cox.
Bedingham brought up his century - from 154 balls with two sixes and 11 fours - when he turned Dillon Pennington off his legs for two, but Jack Burnham on nine had no answer to a lifting delivery from Pennington and the nick was taken head-high by Cox.
Ned Eckersley edged a Leach away swinger to Cox after making eight and Brydon Carse had only a single to his name when he cut Pennington to Ed Barnard at point.
Tongue brought Bedingham's fine knock to an end on 121 when he was lbw working the ball to leg. He batted for 183 balls and hit two sixes and 13 fours. Barnard wrapped the innings up when Ben Raine, after a quickfire 16, holed out to deep backward square.
Potts quickly made a breakthrough with Daryl Mitchell falling to a superb one-handed reflex catch in the gully region by Carse.
Libby looked in good form and greeted the introduction of Raine with three boundaries in an over. Tom Fell also looked composed at the crease and the second wicket pair added 67 in fluent fashion in just 15 overs.
But Potts returned to the attack and had Fell leg before for 21 and Gareth Roderick completed a pair when shouldering arms and being bowled by Chris Rushworth.