The $US1 million ($NZ2.04 million) tournament opens on May 17 and New Zealand's first game is against Bangladesh at Chelmsford.
Stewart said that New Zealand would have to adapt to the different pitches and grounds it would play on in the tournament.
``But Nathan Astle is an exceptional one-day player and he is coming to terms with test cricket. I have been impressed with Stephen Fleming since he came in and took over the side.
``Daniel Vettori also has a good future in test cricket.''
Stewart said New Zealand was highly regarded in the world one-day arena and Chris Cairns was always a threat on the days he got going with the bat.
Meanwhile, pace bowler Simon Doull returns to the New Zealand cricket team for its next assignment, an international knock-out event in Bangladesh next month. Doull, who has regained fitness after a groin strain kept him from Commonwealth Games team selection, replaces fellow medium-fast bowler Chris Drum, who is now on the injured list.
National selection panel convener Ross Dykes said Drum's injury, while minor, was the result of an incorrect element in his bowling action.
``We felt it prudent to give him time to recuperate from the injury and work on correcting the problem with his action.''
Doull's inclusion is subject to passing a fitness test prior to the team's departure.
Still on the unavailable list recovering from injury are Dion Nash (back), Cairns (knee), Llorne Howell (shoulder), and Gavin Larsen (back).
The team leaves for Dhaka on October 11 with build-up matches in Sydney before its first game, against Zimbabwe, on October 24.
New Zealand squad:
Stephen Fleming (captain), Geoff Allott, Nathan Astle, Chris Harris, Craig McMillan (Canterbury); Mark Bailey, Simon Doull, Alex Tait, Daniel Vettori (Northern Districts); Matthew Bell (Wellington); Matthew Horne, Paul Wiseman, Shayne O'Connor (Otago); Adam Parore (Auckland).