Alastair Cook & Haseeb Hameed available for counties until July
England Test openers Alastair Cook and Haseeb Hameed can play all of their counties' fixtures before July's first Test against South Africa, the England and Wales Cricket Board has confirmed.
Essex's Cook, 32, and Lancashire's Hameed, 20, along with Durham's Keaton Jennings, are available for every One-Day Cup and County Championship match.
Pacemen James Anderson and Stuart Broad can feature in the majority of games.
England Test captain Joe Root can play three One-Day Cup matches.
Several members of England's Test side will be away with the one-day team for the Champions Trophy which runs from 1-18 June.
Yorkshire's Root is available for only one four-day game before the South Africa series, as the ECB has allowed all of England's Test squad to take part in the first ever day-night round of County Championship fixtures, starting on 26 June.
It is hoped it will give the players more experience of the pink balls that will be used for England's inaugural day-night Test against West Indies at Edgbaston in August.
Andrew Strauss, director of England cricket, said: "This was always going to be a difficult summer in terms of managing the workload on our England players, with such a hectic schedule including the Champions Trophy as well as seven Tests, followed by an equally busy winter in Australia and New Zealand.
"We appreciate all of this causes disruption for counties and frustration for their supporters, and we are grateful to them for seeing the big picture in appreciating the need for us to ensure that key players remain in the best possible condition for the challenges ahead."
England player availability
One-day squad, One-Day Cup
Moeen Ali - available for Worcestershire matches against Lancashire (10 May), Warwickshire (12 May) and Durham (14 May).
Jonny Bairstow, Adil Rashid, Joe Root - available for Yorkshire against Durham (3 May), Northamptonshire (10 May), Warwickshire (14 May).
Liam Plunkett, David Willey - available for Yorkshire against Northamptonshire (10 May), Warwickshire (14 May).
Jake Ball, Alex Hales - available for Nottinghamshire against Derbyshire (2 May), Durham (11 May), Lancashire (14 May).
Jason Roy - available for Surrey against Essex (12 May) and Hampshire (14 May), as he is not expected to return to IPL after England's two ODIs against Ireland.
Mark Wood - available for Durham against Nottinghamshire (11 May) and Worcestershire on (14 May).
Steven Finn - available for Middlesex for all One-Day Cup and County Championship matches from 8 May.
Ben Duckett - available for Northamptonshire for all One-Day Cup and County Championship matches from 8 May.
Sam Billings (Kent), Jos Buttler (Lancashire), Eoin Morgan (Middlesex), Ben Stokes (Durham), Chris Woakes (Warwickshire) - Indian Premier League.
James Anderson - available for all Lancashire's One-Day Cup fixtures, and their County Championship games against Yorkshire (19-22 May & 2-5 June), Middlesex (9-12 June) and Warwickshire (26-29 June - day-night round)
Gary Ballance - available for all cricket in One-Day Cup and County Championship for Yorkshire
Stuart Broad - available for all Nottinghamshire's One-Day Cup fixtures, and for County Championship matches against Glamorgan (19-22 May), Gloucestershire (26-29 May), Leicestershire (19-22 June) and Kent (26-29 June - day-night round). Not available for County Championship games against Derbyshire (2-5 June) or Gloucestershire (9-12 June).
Alastair Cook - available for all cricket in One-Day Cup and County Championship for Essex.
Haseeb Hameed - available for all cricket in One-Day Cup and County Championship for Lancashire.
Keaton Jennings - available for all cricket in One-Day Cup and County Championship for Durham.
Chris Jordan and Tymal Mills (both Sussex) - available for all One-Day Cup and County Championship matches when they return from the IPL.*
*NB Mills has only played Twenty20 cricket since 2015.