Record-breaking price increases for US mobile phone services helped push a key inflation gauge above expectations, potentially cementing the Federal Reserve's decision to raise interest rates next week.

Data released on Friday by the Bureau of Labor Statistics showed the core consumer price index, which excludes food and energy, rose 0.3% month-over-month in August, exceeding the 0.2% median forecast from a Bloomberg survey. Wireless phone service prices alone jumped 5.9% during the month, contributing roughly 0.1 percentage points to the core CPI reading.

This particular component primarily reflects prepaid and monthly plan pricing offered by mobile carriers. Economists at Bank of America, Barclays, and Pantheon Macroeconomics have pointed to recent pricing adjustments by major operators such as AT&T and T-Mobile US as the likely driving force behind the surge. The Bureau of Labor Statistics declined to elaborate on how exactly these operator changes influenced the data.

Earlier this year, AT&T announced plans to raise prices on certain plans starting in August. Meanwhile, T-Mobile recently discontinued several legacy plans, leaving some consumers facing higher costs. Despite these one-time distortions in the underlying inflation figures, many Fed watchers still view the case for a rate hike as valid.

"Granted, the mobile phone services index contributed 10 basis points to core CPI today, and if you strip that out, the month-over-month core reading would be 0.20%," said Omair Sharif, president of Inflation Insights LLC. "But I don't think the Fed has the luxury at next week's meeting to parse the data in such a granular fashion."

Energy and food costs added to the overall picture, with the broader CPI landing at 3.4% year-over-year in August, reinforcing the prevailing market expectation that policymakers will deliver another rate increase when they convene next week.