Defending world champion Sebastian Vettel New Delhi - Agencies Defending world champion Sebastian Vettel topped both practice sessions at the Indian Grand Prix Friday as he bids for his fourth win in a row and a historic third straight drivers title. The Red Bull driver, 25, who seized the championship lead at the last race in South Korea and is seeking to become Formula One\'s youngest triple champion, scorched a fastest lap of one minute and 26.221 seconds in the second session. He finished ahead of his Australian team-mate Mark Webber with Ferrari\'s Fernando Alonso, the long-time championship leader now supplanted by Vettel, third fastest. But Vettel later rejected all suggestions that Sunday\'s race will be a private duel between him and Webber. \"It\'s not between Mark and myself, I think it\'s between all of us,\" said Vettel. \"I think Friday is always difficult on a day like this and on a circuit like that because when you are out doing your new tyre run, track improvement is quite big. \"I wouldn\'t be surprised if tomorrow looks a little bit different, but we\'ve had worse Fridays so I\'m quite happy.\" The two drivers were six-tenths of a second clear of the field after both sessions with Webber close enough to justify his defence of his right to fight his German team-mate for victory in his own bid to win the world championship. The Australian may lie fifth in the standings, 63 points behind Vettel, but, with 100 points still up for grabs in the remaining four races, he retains a chance of wrecking Vettel\'s dream of delivering a hat-trick of titles. \"This weekend if I have the chance to win the Grand Prix, I\'ll go for it,\" said Webber. \"Mathematically I have a chance (to be champion). So, if I\'m in the lead, I\'m not pulling over for anyone.\" Alonso predicted a tighter battle for qualifying on Saturday. \"This is an interesting circuit -- after the longest straight, there\'s a combination of high-speed corners which are very nice to drive,\" said the Spaniard. \"Today the track was still very dirty, which is usually the case at new tracks that aren\'t used very often. Tomorrow, when it will deliver more grip, it will be even more fun.\" Nico Rosberg was fourth in the leading Mercedes ahead of Kimi Raikkonen of Lotus and the two McLarens of Britons Lewis Hamilton and Jenson Button. Nico Hulkenberg was eighth for Force India ahead of Romain Grosjean in the second Lotus and Bruno Senna for Williams. On a bright, dry day with a temperature of 28 degrees Celsius, the conditions were near-perfect as Vettel continued his irresistible form in Asia by topping the first session from Button, and staying ahead of the pack in the second. Wins in Singapore, Japan and South Korea have lifted Vettel to a narrow, six-point lead in the standings but with strong momentum and growing belief that the German can seal the title over the last four races. Both Alonso and Hamilton, who will leave McLaren for Mercedes next year, also impressed with heavy fuel loads, but there is widespread sentiment that Red Bull are back in the groove that brought them title doubles in 2010 and 2011.