By Nivedita Balu

TORONTO (Reuters) - Canada's big six banks will probably set aside a total of C$4.5 billion in loan loss provisions in the third quarter, analysts predicted, up nearly 27% from a year ago, as insolvencies rise and lenders prepare for credit card and other delinquencies in a challenging economy.

The banks, which control a big chunk of the country's banking market share, could feel the brunt of elevated borrowing costs, slowing employment and possibility of a recession weighing on consumer and business sentiment.

"Third-quarter results are likely to reflect a challenged Canadian economy, with banks expected to report sluggish loan growth, while credit costs creep higher," BofA Securities analyst Ebrahim Poonawala said.

Overall, the TSX banking index's 8.3% growth so far this year has underperformed the broader TSX index's 10% gain.

The benefits of Bank of Canada's two rate cuts this year on deposit costs and interest expense are unlikely to be fully reflected in the third quarter, but with mortgage renewals around the corner, three upcoming rate cuts could help ease pressure on credit in the second half of the year.

"With the Bank of Canada being more aggressive than anticipated on rate cuts, we are more concerned about the near-term outlook... there will need to be much stronger-than-anticipated earnings to fuel support for the banks," Jefferies analyst John Aiken said.

US OPERATIONS IN FOCUS

Eyes will be on TD Bank on Thursday, the first bank to report third-quarter results as investors await details of the U.S Department of Justice's investigation into deficiencies in its anti-money laundering program.

TD, which has made a big push into the U.S. over the years through acquisitions, has said it would grow in the region organically through building new branches after its proposal to buy First Horizon failed and the probe has led to a pause in its expansion plan.

Bank of Montreal is also expected to show a rise in loan loss provisions due to a potential loss on a loan to U.S. solar company SunPower.

"The overhang related to its credit performance, sluggish loan growth and U.S. exposure in general will likely persist until after the November U.S. election and the Fed begins to shift towards a rate cutting cycle," National Bank analyst Gabriel Dechaine said. "Patience is required," he noted.

Loan loss provisions are expected to rise at five of the six banks between 28.4% and 45%, while CIBC is forecast to see a reversal of its loan loss provision, according to LSEG data.

(Reporting by Nivedita Balu in Toronto; Editing by David Gregorio)