The world’s biggest watchmaker is also an important supplier of watch movements that power mechanical timepieces. If it cannot sell them, Swatch itself and its customers, from Cartier maker Richemont to independently owned Chopard and Breitling, may face problems.Anti-trust agency WEKO said deliveries of watch movements to Swatch Group’s existing customers would be suspended from Jan. 1, with an exception for small and mid-sized companies of up to 250 staff, until the watchdog reaches a final decision.

The decision creates uncertainty over supplies at a time when Swiss watchmakers face competition from smartwatches and slowing demand in key market Hong Kong. Swiss watch export data on Thursday showed shipments to Hong Kong fell 27% in November.Swatch shares were indicated 1.1% low…