India, Sept. 23 -- McDonald's warned that customer traffic in its key markets could remain flat while inflation stays elevated, sending its shares down as much as 6.5 percent on Wednesday.

The warning came as the fast-food giant detailed its "NEXT" strategy, aimed at restoring growth after several quarters of weaker sales and increased competition from value-focused rivals. McDonald's shares have fallen about 22 percent this year and touched a nearly four-year low of $234.03.

The company announced an $8.5 billion, decade-long support package for franchisees, including about $5 billion through 2030 for rent relief and capital support. McDonald's expects the programme and operational changes to improve restaurant-level efficiency by 250 bas...