With a Korean free-trade agreement in hand, cattle producers will be pushing government officials to challenge restrictions on U.S. beef, a key Montana rancher said Friday.

Bill Donald, Melville rancher and president of the National Cattlemen’s Beef Association, said he expects that within six months trade officials will challenge South Korea’s refusal to accept U.S. beef older than 30 months.

The age restriction has been a hotly contested issue among American ranchers who say there is no scientific reason for it. The free-trade agreement approved by Congress on Wednesday requires South Korea to give the U.S. concerns fair hearing once raised.