The CPI report arrives tomorrow. It could determine whether the Fed hikes rates next week.

A key inflation reading tomorrow could determine whether the Federal Reserve issues its first interest rate hike in more than three years.The August Consumer Price Index report, scheduled for release at 8:30 a.m. ET on Friday, is the last major inflation snapshot Fed officials will receive before announcing their next interest rate decision on Sept. 16. Economists expect prices last month rose 3.3% on an annual basis, reflecting an easing after reaching a three-year high of 4.2% in May.The August report could help Fed officials determine whether the recent easing reflects an ongoing trend, or whether inflation is becoming stubbornly entrenched amid high fuel prices caused by the Iran war. Its primary tool for taming inflation, one of its core mandates, is to raise borrowing costs, which helps cool spending.At the Fed's previous meeting, nearly half of its policymakers said they would support a rate hike later this year.