Australia A 203 for 0 (Harris 100*, Burns 88*) trail Sussex 263 (Rawlins 69, Pattinson 4-60) by 60 runs
Harris finished unbeaten on 100 with Burns on 88 as they added 203 in 49 overs in reply to Sussex's 263 all out in which James Pattinson finished with 4 for 60 and Jon Holland 3 for 49.
Against a Sussex attack missing a number of first-team regulars, Harris and Burns made largely serene progress with Harris bringing up his century from 142 balls in the penultimate over of the day.
Before the tour, Harris had spoken about hoping to be able to pick up his form from the Australian domestic season when he scored more than 1000 Sheffield Shield runs in a summer where he made his Test debut and produced some promising performances. He looked in good touch throughout his stay to enhance his claims to be David Warner's opening partner for the first Test at Edgbaston.
However, for Burns this was also a very significant day as he aims to restate his Ashes credentials. It was his first innings since withdrawing from his Lancashire deal due to chronic fatigue syndrome. He was only cleared to return to action last week then immediately drafted into the Australia A squad and his game looked in good order as he struck 13 boundaries. Along with Harris he is an incumbent Test player and scored 180 in his last outing against Sri Lanka in February.
Earlier in the day, Sussex had put up some stubborn resistance to extend their first innings from the overnight 118 for 5. Abi Sakande fell early to Michael Neser but Delray Rawlins and Adam Rouse added 58 for the seventh wicket. Rawlins struck ten fours and a six in his 69 off 103 balls before being trapped lbw for Holland's first wicket.
The Sussex lower order continued to chip in before Holland wrapped the innings up with a brace of wickets. Josh Hazlewood finished wicketless from 19 overs in his first red-ball bowl since the stress fracture of his back in early January which has kept him out of action until this tour.