Korean government to renegotiate US beef deal
Imports would be delayed until the US responded, he said. The US said the two nations were discussing the issue.
At the weekend, tens of thousands held protests over renewing US beef imports, citing fears of mad cow disease.
More than 200 people were arrested and dozens were hurt as police and demonstrators clashed in the capital, Seoul.
White House spokesman Tony Fratto said on Tuesday: "We're in communication with the [South] Korean government to try to understand their plan.
"We'll continue to work with US industry and our Korean counterparts to ensure that our concerns are addressed."
The beef issue has become a major challenge to new President Lee Myung-bak, with support for him plummeting.