Ireland came out on top in the battle of the unbeaten Group A sides and are looking good to qualify for the latter stages of the tournament now after another last gasp win, this time over host side UAE.
Coach Phil Simmons kept faith with the same starting eleven for the third successive day and on winning the toss, Ireland had no hesitation in batting first.
William Porterfield and Paul Stirling were straight on the attack against Manjula Guruge and Shadeep Silva, Stirling in particular sore on Guruge who leaked 21 runs in his first two overs.
Silva's second over turned out to be a real hammer blow for the Irish however, Stirling bowled for 13 playing around one and then Niall O'Brien bowled for a duck as he missed with an attempted sweep.
Kevin O'Brien joined his skipper in the middle but disaster struck for Ireland soon after when Porterfield came up short trying to scramble a quick single and was run out for 18.
O'Brien was joined by Gary Wilson as the batting side tried to consolidate and this pair went on to do a superb job for their team.
The big hitting O'Brien was given a life by the home side on 22 when Saqib Ali dropped a regulation catch and he made them pay as he and Wilson went on to add a 92-run stand that only ended in the final over.
Boundaries were hard come by on the slow track so the batsmen had to work really hard for their runs, the Railway Union man finishing with 47 (two fours and a six) in dead even time.
His batting partner made it to a superb unbeaten 53 (three fours) that came off just 44 balls, both men drained by their efforts to get their side to a decent total.
Ireland completely lost the momentum in that last over with the dismissals of O'Brien and then John Mooney first ball, managing just five runs from the final six deliveries.
Guruge (2-23) got it right in his second spell while Silva (2-26) and Khurram Khan (0-17 from 4 overs) also bowled well as Ireland closed on 138 for 5.
The reply started in a blaze of action as Muhammad Azam clubbed Tim Murtagh's second ball for 6 and was then out seconds later trying to repeat the dose.
Shaiman Anwar and Khurram Khan picked up the mantle from there and this pair comfortably took the hosts ahead in the contest as Ireland's bowlers struggled.
The introduction of Paul Stirling and Max Sorensen into the attack gave the Irish renewed hope however, Sorensen finally breaking the 53-run partnership by removing the dangerous Khan for 35.
The game swung back Ireland's way when Stirling did for Anwar in the next over and with runs drying up, Sorensen dismissed Saqib Ali to leave the Emirates 72 for 4.
Swapnil Patil was next to go, falling to Dockrell for 14 after he and Rohan Mustafa had added 21 to the home side's cause. Mustafa and Muhammad Shafiq took the score on to 115 before Dockrell tempted the latter into a big hit which was snaffled by Stirling on the boundary and with time running out Ireland had edged back in front.
The 19th over saw the contest really swing- Amjed Javed clubbing Cusack for two big sixes before the bowler gained his revenge by tempting him out just enough for Gary Wilson to send him packing.
Going into the final over the home side needed nine to win with three wickets in hand and Porterfield threw the ball to Johnston who has rarely let Ireland down in his 192 cap career, and proved just the man for the job.
Johnston's steady stream of yorkers saw UAE getting themselves into an almighty tangle trying to claw back the deficit and lost two of their last three wickets to frantic run outs before Johnston cleaned up number 11 Guruge first ball to send the Irish top of the group with a five run win.
Another battling performance from Porterfield's men and the side fully deserve their two day break until Wednesday when they take on USA.