```cmake
set(SITK_CMAKE_MINIMUM_REQUIRED_VERSION "3.16.3")
set(SITK_CMAKE_POLICY_VERSION "3.16.3")

if("${CMAKE_VERSION}" VERSION_LESS_EQUAL "${SITK_CMAKE_POLICY_VERSION}")
  set(SITK_CMAKE_POLICY_VERSION "${CMAKE_VERSION}")
endif()
```

Set CMake Policy version up to 3.20
user
```cmake
set(SITK_CMAKE_MINIMUM_REQUIRED_VERSION "3.16.3")
set(SITK_CMAKE_POLICY_VERSION "${SITK_CMAKE_MINIMUM_REQUIRED_VERSION}...3.20")
```
assistant