Russia"s central bank is expected to raise its key interest rate by a hefty 100 basis points to 8.5% on Friday as inflation hovers near a six-year high and geopolitical risks rattle markets, a Reuters poll suggested on Monday. The central bank has raised rates six times this year but failed to rein in inflation, its main area of responsibility, which has kept on accelerating, denting living standards and prompting President Vladimir Putin to call for preemptive steps. Twenty-three of 28 analysts and economists polled by Reuters predicted that Russia will raise the key rate by 100 basis points to 8.50% (RUCBIR=ECI), its highest since September 2017 and above the consumer inflation rate of 8.40% in November. Many analysts revised their calls for 25 or 50 basis point hikes they voiced in the previous poll last month after inflation, which the central bank targets at 4%, accelerated to 8.4% in November, its highest since early 2016. read more Governor Elvira Nabiullina told the Reuters Next conference earlier this month it would be a harmful policy mistake to underestimate inflation risks, saying her bank was planning to consider raising rates by up to 100 basis points on Dec. 17. read more "It is crucial that CBR tightens its policy sooner than later," Sova Capital said in a note, predicting a 100-basis-point hike this week and another 50-basis-point rise in early 2022. Nabiullina said options to hold the rate or raise it by just 25 basis points looked unlikely at the Dec. 17 board meeting. Five experts in the Reuters poll said the bank will opt for a 75-basis-point hike. "Inflation is close to its peak so the rate hike this week could be the last one in the cycle," Vladimir Osakovskiy, chief economist at Bank of America in Moscow, said. He predicted a rate hike to 8.25% on Friday. A dovish signal could be positive for the rouble, which for now is more affected by geopolitical factors, Osakovskiy said. Reporting by Andrey Ostroukh; additional reporting by Elena Fabrichnaya; editing by Andrew Heavens Our Standards: The Thomson Reuters Trust Principles.