Sri Lanka make bright start in victory bid
Tharanga Paranavitana was unbeaten on nine and Dinesh Chandimal was on 14, with Sri Lanka still requiring 243 runs more in a minimum of 66 overs to take the series 2-0.
Sri Lanka are eyeing their first Test series win in three years since beating New Zealand 2-0 at home in 2009.
Mahela Jayawardene's home team defeated Pakistan by 209 runs in the first Test in Galle before the rain-hit second match in Colombo was drawn.
Earlier, Asad Shafiq remained unbeaten on 100 as Pakistan declared their second innings at 380-8 half-an-hour before lunch to attempt a series-levelling win.
The tourists, who resumed at the overnight score of 299-8, added 81 runs in 24.4 overs in the final morning.
Shafiq, the top-scorer in the first innings with 75, hit nine boundaries in his second Test century when skipper Misbah-ul Haq declared as soon as the landmark was reached.
Adnan Akmal, batting with a hairline fracture in his left hand, scored a gutsy 35 not out as he put on 81 for the ninth wicket with Shafiq.
Left-arm spinner Rangana Herath was Sri Lanka's most successful bowler with 4-99 in the second innings. Fast bowler Dilhara Fernando claimed 3-74.