The Royal Bank says low oil prices will make 2016 more challenging for Canada's economy than previously thought.

The bank has lowered its forecast for this year's gross domestic product to just 1.7 per cent.

That's down from RBC's December forecast of 2.2 per cent growth this year.

RBC continues to expect Canada's economic growth will be underpinned by solid consumer spending, stronger exports and stimulus from the federal government.

But it says oil prices were lower than estimated early this year and they will weigh on business investment.

The bank's latest quarterly economic forecast estimates the average price of West Texas Intermediate crude will be US$40 per barrel this year — $12 less than its previous forecast in December.

RBC is also lowering its 2017 oil price estimate to $57 per barrel from $62.