WELLINGTON - New Zealand's planning for next year's World Cup further crystallised on Tuesday with the decision to maintain 12 of their one-day side for their two Twenty20 matches against West Indies. Only pace bowler Kyle Mills and top-order batsman Kane Williamson were released from the 14-man one-day squad, who conclude their series against the visitors in Hamilton on Wednesday, for the Twenty20 clashes in Auckland and Wellington."We are keen to keep this group together but are mindful of the strong performances from a number of other players," national selection manager Bruce Edgar said. "We are fortunate to be in a position to have a range of quality players to choose from." New Zealand hold a 2-1 lead over the visitors in the one-day series after two impressive batting displays that included a world record for the fastest international century by Corey Anderson.The 23-year-old Anderson blasted a century off 36 balls as New Zealand smashed 283-4 in 21 overs in Queenstown to win the rain-effected third one-dayer, while a more balanced approach saw them score 285-6 in 50 overs in the fourth match in Nelson. The victories were cemented with a core nucleus of players all combining to produce when it was required. The New Zealand batting line-up is ultra aggressive with Jesse Ryder and Martin Guptill opening, while Kane Williamson's patient approach will allow the side to build their innings around him before Ross Taylor, captain Brendon McCullum and Anderson take over in the middle order. Swing bowler Mills provides the anchor role to restrict the scoring in the opening power-play, while left-arm quick Mitchell McLenaghan's job is to take wickets, even if his economy rate is more than 5.6 runs an over.NEW ZEALAND T20 SQUAD: Brendon McCullum (captain), Corey Anderson, Martin Guptill, Mitchell McClenaghan, Nathan McCullum, Adam Milne, Colin Munro, James Neesham, Luke Ronchi, Jesse Ryder, Tim Southee, Ross Taylor.