Daryl Mitchell hit his seventh century of the season and then Worcestershire skipper Joe Leach struck two early blows after Durham were set a 370 target in the Specsavers County Championship clash at New Road.
Promoted Worcestershire are looking to add the Division Two crown and, after resuming on 157-3, Mitchell and George Rhodes scored freely in extending their partnership to an unbroken 111 in 24 overs.
Mitchell completed his 134 ball hundred with a cover drive for three off slow left armer Liam Trevaskis.
It contained nine fours and was greeted with a standing ovation.
Rhodes went to his second half century off the campaign at which point the declaration came with Worcestershire on 242-3.
Mitchell ended unbeaten on 123 to give him a season’s aggregate of 1266 Championship runs at an average of 55.04 while Rhodes remained 51 not out.
Leach then got to work with the ball after Durham had been left 11 overs batting before lunch.
He trapped Cameron Steel (5) lbw to the final ball of his first over and then Jack Burnham (11) offered no stroke and fell in the same manner.
Keaton Jennings, in his final innings for Durham before joining Lancashire, was unbeaten on 17 out of 42-2 at the interval.