US derivatives regulator the Commodity Futures Trading Commission said on Wednesday that it would put on hold the self-certified listing for a Chicago Mercantile Exchange contract that would have enabled 24/7 trading in crude oil futures as soon as tomorrow.

The action pushes back exchange operator CME Group‘s planned launch of its new 10-Barrel WTI Crude Oil futures contract, which CME had said would begin on August 30 pending regulatory review. The contract is cash-settled, listed on NYMEX, and sized at one-tenth of CME’s Micro WTI futures contract already in place.

CME announced the product on June 11 as part of a broader 24/7 commodities push that also includes round-the-clock trading in its 1-Ounce Gold futures.

The CFTC signalled concern on June 22, when the Commission issued a request for public comment on making standard futures contracts tradable 24/7, asking for input on implications for manipulation, surveillance, position limits, clearing, and effects on physical energy markets.

“As registered entities extend trading hours and introduce new contract designs, a clear, data-driven record will help the Commission better understand these developments’ implications and impact in the market,” CFTC Chairman Michael S. Selig said.

The stay marks the first direct regulatory action against CME’s 24/7 energy expansion since the exchange announced its plans.