July 9 (Reuters) - The U.S. Commodity Futures Trading Commission (CFTC) said on Thursday it would exercise its authority to stay the listing of a contract that would have allowed CME Group CME.O to initiate 24/7 trading on crude oil futures as soon as Friday.

The move comes after CME sought to self-certify the contract on July 8, despite an ongoing public comment period on the extension of standard futures contracts to round-the-clock trading, including crude oil.

CME Group, the world's leading derivatives marketplace, had announced in June that it would offer 24/7 trading in some crude and gold futures contracts, pending regulatory review.

CFTC Chairman Michael Selig said the commission was still examining whether 24/7 trading of futures contracts on various asset classes was consistent with its statutory Core Principles.

"We do not take a one-size-fits-all approach to 24/7 trading," Selig added in a statement.

The commission said its regulations offer exchanges two methods to list contracts — self certification and seeking a review and approval. "CME made simultaneous, but separate filings under both provisions."

CFTC said it would conduct a thorough review of the product filings and bar CME from listing such contracts before determining they comply with the Commodity Exchange Act and Commission regulations.