Low natural resource prices have prompted Standard & Poor's to downgrade Saskatchewan's credit rating to double-A plus from triple-A.

The agency says persistently low natural resource prices, in particular oil and potash, have had and are expected to continue to affect the province's budget.

The Saskatchewan government ran a deficit in the fiscal year that ended March 31 and is projected to have a deficit this year too.

The credit rating agency's negative outlook also says in the next two years there is a one-in-three chance the province will not be able to meet its budget targets of low or no growth in operating expenditures.

It further says that Saskatchewan's cash reserves have fallen notably and cannot be used to cover deficits.

The report also says Saskatchewan's financial results are less volatile than those of other provinces with resource-based economies such as Alberta and Newfoundland because of the diversity of its resource base.