Any spending reductions will be reflected in the Welsh government's budget, under a spending formula.
Commenting on Twitter, Welsh government Finance Minister Jane Hutt said this was "more bad news for Wales".
But the UK government said Wales was "thriving" under "our long-term plan" and must contribute to the savings.
Chancellor George Osborne is exempting spending on health and schools in England, which limits the impact of any cuts on Wales.
Defence and overseas aid budgets are also being protected from the cuts, of up to £20bn, to be announced when Mr Osborne unveils his spending review in November.
Ms Hutt said: "The late timing of the spending review makes the challenge of managing the impact of further austerity even greater.
"£20bn cuts to public spending on top of £12bn of welfare cuts set out earlier this month."
"Cuts on the back of successive reductions to our Budget over the last five years have seen £1.3bn taken out of vital public services in Wales," Ms Hutt added.
The UK Treasury has said it wants unprotected departments to draw up two separate models, to plan for cuts of 25% and 40%.
Responding to Ms Hutt's criticism, a UK government spokesperson said: "Our long-term plan has created the conditions under which Wales is thriving.
"This spending review is the next step in our plans to eliminate the deficit, run a surplus and ensure Britain lives within its means.
"All parts of Britain will need to play their part in making us more secure through finding efficiency savings whilst ensuring that spending is targeted at frontline services."
Welsh ministers have criticised plans to ask some UK government departments to prepare for cuts of either a quarter or two fifths of their budgets by 2020.