Thames Valley Police says it may have to merge services with surrounding forces to meet an extra £3.7m cut imposed by the government.
The force plans to share forensics, legal services and IT systems with Hampshire, Surrey and Sussex.
Thames Valley now has to cut £8.2m this year, £18.1m next and £11.9m in 2012.
Chief Constable Sara Thornton said she would do "everything she can" to protect front-line services.
Further savings will come from a variety of budgets, including agency staff, overtime and consultancies.
The report will go before Thames Valley Police Authority for approval on Friday.
Last year there were concerns that Thames Valley would have to cut up to 166 posts as it tried to save £11m from its annual budget.
However, only 50 redundancies were agreed, and the force managed to find funds to recruit an extra 27 police officers.