Worcestershire 180 and 117 for 3 (Libby 64*) need another 244 runs to beat Sussex 284 and 256 (Alsop 72, Coles 68)
Sussex go into the final day of their County Championship fixture against Worcestershire with their noses in front after dismissing New Zealand stalwart Henry Nicholls and number four batter Kashif Ali late in the evening session.
An 81-run second-wicket stand from Nicholls and opening batter Jake Libby had steered the visitors into a decent position before Nicholls' mistimed pull shot found the gloves of wicketkeeper John Simpson and gave Sussex debutant James Hayes his maiden first-class wicket.
England's Ollie Robinson snagged the day's final wicket in the penultimate over, extracting a thick edge from Ali, which fell to the grateful hands of James Coles at third slip.
Three down for 117, Worcestershire require a further 244 runs to win after twin fifties from Tom Alsop and Coles, and some tail-end bashing helped the hosts to a second innings lead of 360.
Any chance of a Worcestershire victory likely rests with Libby, who remains unbeaten on 64 (105 balls), accompanied by nightwatchman Ben Allison on three (6). Libby kept a steady head while wickets fell around him and cashed in on some loose Hayes deliveries to pass fifty with a thrashing cut shot.
Ari Karvelas took Sussex's only wicket of the Worcestershire innings, bowling Gareth Roderick for four with a dipping yorker that snuck beneath the opener's bat.
The home side secured its dominant position in the morning session with a sturdy batting performance from Alsop and Coles. Both began the day in the twenties and took advantage of some loose deliveries from Worcestershire's fast bowlers, striking 21 boundaries between them as the Sussex lead sailed past 250.
All-rounder Coles was particularly strong through the leg side, passing fifty with a forceful clip for four off Ben Gibbon in the 39th over. Alsop was equally convincing and reached his half-century one over later against the same bowler.
Their 125-run partnership took Sussex from a potentially dangerous situation to a likely insurmountable lead before both were dismissed lbw before the lunch break. Coles fell for a 132-ball 68, shouldering arms to an inswinger from Ben Waite before his batting partner played back to a sharp-spinning Fateh Singh delivery for 72 (136).
Their dismissals led to something of a mini-collapse for Sussex, who lost four wickets for 45 runs around the lunch break as captain Simpson 13 (45) and Hudson-Prentice were both caught behind off the bowling of Allison, for took 3-52 in the innings.
Despite the flurry of wickets, Sussex at 188-seven had extended its lead past 300 and now looked in the mood to attack as first-innings centurion Jack Carson combined with Robinson for a fiery rearguard stand of 47.
Both targeted left-arm spinner Singh, who the former hit for consecutive fours in the 66th over, and the latter crashed for a long, straight six in the 72nd.
The fun came to an end soon after when both batters sprinted to the same end after a single and Robinson was run out for a feisty 30 (31). Singh, who finished with admirable figures of 3 for 58 from his 17.4 overs, took the final two Sussex wickets in quick succession as Sussex were dismissed for 256. He first bowled Karvelas for a single before last man Hayes edged a turning delivery to second slip.
