Alastair Cook, England's Test and ODI captain, has been omitted from England's 30-man provisional squad for the World Twenty20 that starts in April in the Caribbean. Cook's new ODI opening partner, Craig Kieswetter, has been included, alongside Peter Trego and Michael Lumb, after their success on the England Lions tour to UAE.

Cook's omission came as something of a snub after he was named in the recent Twenty20 party that played two matches against Pakistan in Dubai, and although his accumulatory style is not best suited to the cut and thrust of the 20-over format, he showed impressive form for Essex in last season's Twenty20 Cup, and was England's most fluent batsman with a brisk 64 in their 50-over victory against Bangladesh in Dhaka on Sunday.

Cook himself had been unaware that the 30-man squad was imminent when asked about it after the first ODI, but said he hoped he had done enough to demonstrate that he has what it takes to succeed. However, according to Geoff Miller, the national selector, who met with England's coach Andy Flower prior to the team's departure for the UAE, he is still some way short of meriting a place in the set-up.

"We didn't think Alastair was a 20-over player so consequently he wasn't selected," said Miller. "He knows the decision and he's obviously very much improving in 50-overs, and that might develop his Twenty20 too. But there's a dramatic difference between 50-over cricket and Twenty20. We don't feel he has gone over that mark to be part of our Twenty20 squad, but that does not mean he's out of it [for good]."

England's spinner, Graeme Swann, who has been named in the 30-man party, said before the announcement that the gulf between the formats was growing. "I think the games are too different to be honest," he said. "The games in Dubai, we focussed on those as our practice for the World Twenty20. I think 50-over and Twenty20 are completely different games these days. Certainly as a spin bowler, every single ball you know guys are going to try to hit you for four or six, whereas in 50-over cricket you can try to put a decent spell together."

Lions pacemen Steven Finn and Chris Woakes have both included, while Sajid Mahmood holds his place despite struggling in his recent Twenty20 outings for England against South Africa. There is no place, however, for James Foster, Robert Key and Graham Napier, all of whom featured in the 15-man party for the 2009 tournament in England.

Owais Shah and Ravi Bopara, who are both set to go to the IPL but did not feature in England's squad for the recent T20s against Pakistan, are both included - and for Bopara, it is his first mention in an England squad since he was dropped for the Ashes decider at The Oval in August, after struggling through the first four Tests of the series. He has since been in New Zealand, rediscovering his form in their domestic Twenty20 tournament.

"Ravi's been reassessing himself," said Miller. "He had a bit of a torrid time; he knew that. He's gone away, gone abroad and looked after his career, and done really well. He's a vital part of our squad, and we still think a lot about him. So when he comes back we'll have a look and see where he is."

Shah's return is conceivably his last chance in an England career that dates back to 2001. He played 50 consecutive ODIs up to and including the ICC Champions Trophy in South Africa last September, but was outspoken in his criticism of the selectors after being dropped for the bilateral series in South Africa that followed soon afterwards.

"We know he's a quality player," said Miller. "He had a bit of a rough time. We needed to see a little bit more so left him out [recently] but we still feel he has something to offer. He's going to the IPL, so [we hope] he can put in a few performances there."

Another interesting conundrum awaiting the selectors is the final availability of Kevin Pietersen, whose wife Jessica is due to give birth to their first child around the time of the tournament in early May.

"We've had discussions with Kevin," said Miller. "As you know, I'm a great advocator of people being solid family-wise and I have no argument about that. I'm prepared to allow him to go home. We're talking about the birth of a child here and we don't know when that's going to be, so we'll play it by ear. Kevin's absolutely fine with the situation."

"All players named have shown their ability in the shortest form of the game and the selectors have some difficult decisions to make when reducing the squad to 15 players," Miller added. "We have a number of young players knocking on the door which underlines the depth in talent currently available and I know all concerned will be hoping they make the final squad for what is a highly anticipated tournament."

Full Squad Paul Collingwood (capt), James Anderson, Ian Bell, Ravi Bopara, Tim Bresnan, Stuart Broad, Steven Davies, Joe Denly, Steven Finn, Craig Kieswetter, Michael Lumb, Sajid Mahmood, Dimitri Mascarenhas, Eoin Morgan, Graham Onions, Kevin Pietersen, Liam Plunkett, Matt Prior, Adil Rashid, Owais Shah, Ajmal Shahzad, Ryan Sidebottom, Graeme Swann, James Tredwell, Peter Trego, Jonathan Trott, David Wainwright, Chris Woakes, Luke Wright, Michael Yardy.