Set an improbable 438 for victory after the tourists declared their second innings at 333 for seven in the afternoon session, the home side reached the close of play at 98 for two with opening batsman Devon Smith leading the way with an unbeaten 59.
While the pitch has held up well over the four days, it is the English who remain favourites to complete their first-ever Test match victory in Antigua, especially with the threat posed by their slow bowlers, even the part-time ones.
Kraigg Brathwaite was the early casualty, fending off a lifting delivery in Stuart Broad's first over to Root.
England's rush for runs in the afternoon session resulted in a declaration at 333 for seven, Gary Ballance getting to 122, his fourth Test century.
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Playing in just his ninth Test match, the Zimbabwe-born left-hander got good support from Root and Ben Stokes in continuing to dominate a deflated Caribbean bowling attack in the morning, 108 runs coming in the two hours' play for just the loss of Root's wicket.
"It was tough going. You really had to grind it out in these conditions."
Ballance and Root had extended their overnight fourth-wicket partnership to 114 when the right-hander played on to fast-medium bowler Jason Holder for the second time in the match.
His knock of 59 followed a vital contribution of 83 in the first innings.
In conditions tailormade for batting, he was obviously bitterly disappointed at not being able to carry on to three figures.
Reputed as a fluent stroke-maker, Ballance's innings was a determined, watchful effort.
He faced 250 deliveries in just over five hours at the crease, stroking 11 fours and two sixes before the quest for quick runs brought about his demise to the persevering Benn.