Australia were on the verge of a four-day victory in the final Test and a series clean sweep after a Sri Lankan batting collapse on the third day at the Sydney Cricket Ground today. At close, Sri Lanka were a shaky 225 for seven and leading by 87 runs with two days left with Dinesh Chandimal on 22 and Rangana Herath not out nine. For a time it looked as if Sri Lanka, well beaten in Hobart and Melbourne, could make a contest of it as Dimuth Karunaratne and skipper Mahela Jayawardene almost wiped out the 138-run innings deficit with a century stand before wickets tumbled.Earlier, Wade scored a thrilling unbeaten century as Australia declared to lead Sri Lanka by 138 runs on the first innings. Australia had declared their first innings at 432 in reply to Sri Lanka's 294.PTI/1835 HRS