First Minister Carwyn Jones has asked his Conservative and Liberal Democrat opponents to "behave responsibly" on the Welsh budget amid spending cuts.
He urged them to "work constructively" with the Labour-Plaid Cymru assembly government after claims that Wales faces a cut of £1.8bn over four years.
Tories said they would be constructive, but called his comments "a bit rich".
Lib Dems welcomed "a more mature approach" but said they would hold the assembly government to account.
The assembly government's draft budget for 2011-12 will be published on Wednesday 17 November, and will be debated the following January, ahead of expected final approval in February.
The Tories and Lib Dems are in coalition in the UK government but are in opposition in the Welsh assembly.
Mr Jones said: "These are exceptional times for Wales. The £860m worth of cuts we were informed about last week was a real hammer blow".
Mr Jones said his government would "act responsibly given the hand we were dealt by the Tory/Lib Dem government" and would look "to protect community and secondary health services, schools and skills".
"These are not just exceptionally difficult times for the Welsh government, however. The current situation also puts an onus on opposition parties in the assembly to behave responsibly in how we decide on our budget.
"The ritualistic opposition-for-opposition's sake type of politics which usually comes into play at this time of year would be wholly inappropriate in the coming months, as we seek to deal with the cuts that have been imposed on us.
"That is why I am calling on the leaders of the Welsh Conservatives and Welsh Liberal Democrats to work constructively with us in the assembly in the weeks ahead to ensure we make this budget process as painless as possible for the people of Wales."
Conservative finance spokesman Nick Ramsay said: "This is a bit rich considering Labour-Plaid's partisan rhetoric over the Spending Review and their refusal to acknowledge what was a fair settlement.
"As a constructive opposition we are always prepared to work constructively with other parties when it is in Wales' best interests. However, we will oppose the assembly government when it is wrong, as it is over its refusal to protect the health budget from cuts."
A Welsh Lib Dems spokesperson said: "The Welsh people understand that the pain caused by Labour's monumental mismanagement of the nation's finances can't be stopped at the Severn Bridge.
"However, Wales received a better settlement than the UK overall. Despite this, the first minister has taken to playing the victim card with glee, engaging in the very 'opposition-for-opposition's sake' politics he now condemns.
"If he is now suggesting that he will adopt a more mature approach, that is at least progress.
"Throughout the budget process, the Welsh Liberal Democrats will be holding the Labour - Plaid government to account, to ensure that the cuts the Welsh government makes are carried out fairly, with minimum impact on front line services."
Elin Jones, Plaid's director of communications, and the rural affairs minister, said: "In this climate the last thing people want is the old style Labour v Tory Punch and Judy-style politics.
"The danger is that this will distract from the huge challenges we in Wales need to overcoming in the coming years.
"This is why Plaid Cymru is determined over the coming months to put all our efforts into developing an ambitious plan, to protect Welsh jobs and services the best we can from these cuts, and crucially to present a clear and ambitions plan for the coming election, and the coming decade.
"Yes, Plaid will fight for every penny Wales deserves, but people want more than this, they want to know what vision the parties in Wales have for the coming decade as well.
"Plaid's main focus over the coming months will be to present an ambitious plan for these challenging times, we very much hope the other parties will follow our lead."