South Korea had said in April it would ease its zero-tolerance policy on zilpaterol-based drugs, such as Merck & Co Inc's Zilmax, from June.
Son Seong-wan, a director at the food ministry, told Reuters the delay was made upon China's request. It was not immediately clear why China had asked for the extension, he added. South Korea does not import beef from China, and is a major client of Australia, the United States and New Zealand.
"The final announcement is expected to be made around July 17 after internally examining any feedback that we get during the notice period," Son said, adding that the notice period would end on June 17.
The feed additive has been under global scrutiny since a video emerged in the United States showing animals struggling to walk and with other signs of distress after taking a growth drug.
South Korea suspended some U.S. beef imports for more than two months last year after traces of zilpaterol were found in two shipments. Many other Asian and European countries also ban the additive due to concerns about its side effects.
Son said South Korea was likely to allow imports of beef muscle with 1 part per billion (ppb) of zilpaterol and 5 ppb in beef liver.
