The two golfers, both chasing their maiden Sunshine Tour victories, are tied on 19-under-par 197 with 18 holes remaining.

South African professional De Beer, who started the third round in third place, two shots behind overnight leader Sullivan, carded a near-flawless six-under-par 66 on Saturday.

De Beer enjoyed a flawless front nine, making birdies at the first, fourth, eighth and ninth holes for an outward 32. After the turn, he dropped a shot at the 11th but recovered with birdies at the 12th, 15th and 18th for an inward 34.

Sullivan, meanwhile, who began the third round with a one-shot lead at the top of the leaderboard, signed for a flawless 68.

The Englishman made birdies at the second, third and ninth holes for an outward 33 before adding another at the 14th for an inward 35.

Cole Stevens and Estiaan Conradie share third place on 18-under-par 198, while Ryan van der Klis, Graham van der Merwe, Tyran Snyders and Travis Procter are tied for fifth on 17-under-par 199.