Australia finished an unequivocal triumph over Pakistan at the Adelaide Oval on Friday to reach World cup semi-final against ruling champions India.
Pakistan won the toss and batted however was hard and all out in the last over with 213 runs.
Josh Hazlewood took 4/35 for Australia.
The Australian team lost opener Aaron Finch (2) with the aggregate on 15 and withstood a torrid spell from Wahab Riaz (2/54) amidst the chase.
Riaz was unfortunate to have two important catches put down.
Watson imparted a 89-run stand with Steve Smith (65) and unbeaten 68-run stand with Glenn Maxwell (44 not out).
Watson hit a boundary to get Australia to 216-4 in the 34th over.
Australia will play defending champion India in an elimination round at Sydney on Thursday.