Dhananjaya de Silva struck a century as Sri Lanka handed Pakistan a mammoth victory target of 508 before bad weather hit the hosts' chances of wickets in the second Test on Wednesday.Pakistan were 89-1 when bad light stopped play early and stumps were called on day four in Galle with left-handed opener Imam-ul-Haq on 46 and skipper Babar Azam on 26.The arrival of rain ended any chances of play, adding to Pakistan's hopes of a draw to clinch the two-match series, which they lead 1-0.But the tourists will need to make an unprecedented chase - with another 419 runs needed to win - if they are to make it 2-0.The West Indies hold the record for the highest successful Test chase with 418 against Australia in 2003 at Antigua.Sri Lanka, who declared their second innings on 360-8 in the second session after resuming on 176-5, need nine wickets on the final day to end the series level.Spinner Prabath Jayasuriya sent back first-match hero Abdullah Shafique for 16 with debutant Dunith Wellalage taking a good running catch at mid-off before tea.Imam and Azam played with positive intent and took their chances against the spinners to get quick runs in the weather-hit final session of play.The pair hit six boundaries between them and Azam also smashed Jayasuriya's left-arm spin for a six over the mid-wicket region.Earlier, De Silva made 109 before being run out at the non-striker's end and Sri Lanka skipper Dimuth Karunaratne called his batsmen back to the pavilion.De Silva put on a key stand of 126 with overnight partner Karunaratne, a left-handed batsman who battled back pain during his knock of 61.Bad light forces early stumps on day four.All to play for on the final day ??Watch #SLvPAK live on https://t.co/CPDKNxoJ9v (in select