Durham put themselves in a strong position to take victory on day two of the LV= Insurance County Championship game at Seat Unique Riverside.
The hosts reached 459-7 before declaring as Michael Jones, Scott Borthwick, Nic Maddinson and Chris Benjamin all made half-centuries to give Durham a commanding first innings lead.
They then took 3 wickets in quick succession in the final 4 overs of the day before bad light once again brought the day to a close.
In blue sky conditions, Borthwick wasted no time in pushing Durham forward, as he and Jones reached their half centuries before lunch as the hosts wiped out the remaining deficit.
James Coles struck shortly after lunch, removing Borthwick LBW for a fast paced 82, before Jones was caught down the legside by debutant keeper Charlie Tear four short of a century.
Nic Maddinson added 50 run partnerships with David Bedingham and Chris Benjamin before he chopped on for 90 off Faheem Ashraf as Durham pushed towards a declaration.
Coles was the pick of the Sussex bowlers as he took 3 wickets from his 19 overs.
Sussex were made to bat in low light conditions as the day drew to a close, and the Durham attack full advantage.
Ali Orr, Tom Alsop and Tom Clark were all dismissed within 4 overs to leave Sussex with a mountain to climb to save the game.