India beat Ireland by eight wickets at the Cricket World Cup on Tuesday, remaining unbeaten after five matches to clinch its place atop Pool B while stalling Ireland's celebrated push for a place in the tournament quarterfinals. Shikhar Dhawan scored 100 and Rohit Sharma hit 64 in a 174-run opening partnership - its best at a World Cup - as India chased down Ireland's 259 with 13.1 overs remaining. India will stay at atop the pool regardless of the outcome of its last group match against Zimbabwe. Ireland must now beat Pakistan in the last match of the pool round at Adelaide on Sunday, or at least take a point from that game, to have any chance of progressing to the knockout rounds. India achieved its win with the kind of efficiency which has marked its progress through the tournament. After William Porterfield made 67 and Niall O'Brien 75 from 75 balls to give Ireland hope of a competitive total, India took seven wickets for 53 runs. Faced with an early assault on his seam attack by openers Porterfield and Paul Stirling, who took 57 runs from the first nine overs, India captain M.S. Dhoni introduced spin while maintaining attacking fields and clamped down heavily on the run rate. Spinners bowled the next 22 overs, Ireland went from 57-0 after nine overs to 144-2 after 31, and the momentum of the game changed in India's favor. Porterfield, who made the decision to bat on winning the toss, put on 89 for the first wicket with Stirling (42) to set his team's innings on a sound footing. The partnership was the best for any wicket by any team that has played India at this World Cup. Ireland's total was also the highest score by any team against India in Pool B. India has in common with Pool A leader New Zealand the fact it has bowled out its opponents in all five of its matches: Pakistan for 224, South Africa for 177, the United Arab Emirates for 102 and the West Indies for 182. Porterfield batted through the 22 overs when the India spinners reined in Ireland's scoring and was out only two balls after pace returned in the form of Mohit Sharma, caught by Umesh Yadav from a leading edge. O'Brien put on 53 with Porterfield for the third wicket, and 61 with Andy Balbirnie (24) for the fourth. He tried to ensure the Ireland run-rate remained high with an innings of 75 which included seven fours and three sixes. But after Balbirnie, O'Brien had no substanital support as Ireland lost five wickets for 21 runs in fewer than four overs. Mohammed Shami removed Niall O'Brien, Kevin O'Brien and the last man out, Alex Cusack, for 11 to finish with 3-41. But the credit for Ireland's containment belonged to the India spinners who shared 30 overs and took four wickets for 144 at 4.8 runs per over. There was no containing India as it homed in on an undemanding target. Porterfield used five bowlers inside the first 10 overs. Dhawan, who was dropped on 5 and 10, reached his 13th ODI half century from 54 balls and Sharma his 25th from 48 balls. Their partnership ended in the 24th over when Sharma was bowled by Thompson and Dhawan went on to his eighth century from 84 balls. When Dhawan was out in the 28th over, Virat Kohli (44 not out) and Ajinkya Rahane (33 not out) combined in a 70-run partnership to see India home.