Worcestershire produced an excellent response after conceding their second-highest total in matches against Sussex.
Luke Wells followed his 258 in his last appearance at Hove with 155, Luke Wright made 87, his highest Championship score at Hove for nearly two years and David Wiese a rapid 66 before Sussex declared on 579 for 8.
But Worcestershire openers Daryl Mitchell and Brett D’Oliveira prospered after negotiating the new ball to post an unbeaten century stand as they reached 139 for 0 from 44 overs at the close.
Mark Davis, Sussex coach, said: "I thought we batted really well. Luke Wells did superbly again for his 155 but all the way down the order there were good contributions. It was hard work at the start but Harry Finch set the innings up for us and it was great to see Luke Wright in the runs again and playing with freedom.
"I must admit I did expect the ball to do a bit more on that wicket than it has. I thought we bowled well and made good use of the short ball but their openers have got stuck in. We can still win the game, definitely. They is still a long way off the follow-on target and the second day at Hove is normally the best day for batting. We’ll dust ourselves down and go again tomorrow."
Chris Nash, leading Sussex after Wright resigned as captain on Wednesday, was able to employ attacking fields but his five-strong pace attack found a slow pitch as unyielding as Worcestershire’s bowlers had.
Mitchell survived one scare on 14 when he was put down at slip by Chris Jordan off the third ball after tea to make an unbeaten – his sixth half-century against Sussex.
He has hit 15 fours and a six in his 85 not out and although D’Oliveira was more circumspect he gave his partner good support as Nash rotated his seam attack and regularly employed eight men in catching positions without being able to break through on a wicket which has so far shown little evidence of deteriorating.
Just five wickets fell on the second day, three of them after lunch as Sussex pushed towards a declaration.
Wells and Wright had employed a cautious approach at the start of the day and Sussex failed to claim maximum batting points. Wells, 139 overnight, added 16 runs in just over an hour before he came down the pitch in Nathan Lyons’ first over of the day and lost his leg stump to the Australian off-spinner. Wells batted for six hours, faced 288 balls and 22 fours.
Wright batted with the freedom which had been absent during much of his time as captain and looked on course for a hundred. He hit two sixes and two fours off four successive deliveries from Ed Barnard before upper-cutting the next ball to backward point for 87, his highest score at Hove for nearly two years, having added 86 in 16 overs with Michael Burgess.
Burgess lost his off stump to Barnard after lunch for an enterprising 46 but Wiese and Jordan had licence to go for their shots. Jordan used the slog-sweep effectively to take three boundaries off Lyon in one over while Wiese employed the long handle to hit three sixes and eight fours in his 66 off 53 balls.
Worcestershire skipper Joe Leach, the pick of their eight bowlers, had Jordan (37) caught at wide mid-off to end a stand of 91 in 14 overs for the seventh wicket before the declaration came when Wiese failed to clear long on.