Reuben Jeffery, chairman of the Commodity Futures Trading Commission, is set to leave the US futures industry regulator after being offered a senior position at the State Department, according to people familiar with the matter.

The move would leave the CFTC with a key vacancy at an awkward time. It oversees one of the fastest-growing parts of the capital markets yet has struggled with flat budgets and the departure of key figures, including two of its five commissioners.