Rhodri Morgan and Ieuan Wyn Jones share a 200-plus point policy aim
The Labour-Plaid Cymru government in the Welsh assembly is facing calls to axe some of its key policies to "share the burden" of public sector cuts.
The Welsh Local Government Association says parts of the power-sharing deal's 200-plus aims look "unrealistic and unaffordable" after Wednesday's Budget.
Welsh councils said they knew they had "scope for further efficiencies" as Wales' public sector faced a £416m cut.
Ministers say they faced a "significant challenge" in the coming years.
Chancellor Alistair Darling's Budget means the assembly government must find savings of more than £216m in its revenue or day-to-day spending for the financial year 2010/11.
The expected spending on capital or one-off projects will also be down by £200m.
First Minister Rhodri Morgan has said cuts could not be ruled out but he said significant savings had been managed in the past.
The assembly government, which has seen its budget nearly double to around £15bn in the first decade of devolution, said it took a "modicum of comfort" that losses were not as bad as some forecasts.
Ministers in the devolved Labour-nationalist coalition pleaded with the Treasury to spare their administration from efficiency savings that could have cost it up to £292m in revenue spending, almost £100m more than it must now find.
Chancellor Darling's budget cuts £400m from Wales' public sector
The power-sharing deal between Labour and Plaid Cymru, known as the One-Wales document, was hammered out after the assembly elections in May 2007 left Labour short of an overall majority and Plaid Cymru as the second-largest party.
The 43-page agreement pledges "a progressive, stable and ambitious programme for government over this assembly term," with Plaid Cymru leader Ieuan Wyn Jones as Mr Morgan's deputy.
The Welsh Local Government Association (WLGA) said many of the proposals by the Labour-Plaid Cymru government in the assembly now looked "unrealistic and unaffordable in the current climate".
It warned that the priority must be protecting key public services.
Cardiff councillor Rodney Berman, the WLGA's finance spokesperson, said: "Local government has embraced the efficiency agenda more than any other sector, with councils achieving millions of pounds of recurrent efficiency savings in recent years.
Labour and Plaid Cymru share power at the Welsh assembly
"However, councils are already squeezing everything they can out of the system, making savings wherever they can and being forced into taking some very difficult and unpopular decisions to make ends meet, including job losses."
Pembrokeshire councillor John Davies, the WLGA's leader, said: "We recognise that there is scope for further efficiencies, as there is across all parts of the public sector, but the assembly government should not to assume that further efficiencies will be easy to achieve or deliverable in the short term."
The WLGA said the chancellor's Budget Report suggested "worse to come in 2011-12 and beyond".
The chancellor's budget came as it was revealed unemployment in Wales rose to 108,000 in the three months to February, or 7.5% of the workforce.