Seoul agreed in April to allow imports of U.S. beef from all ages of cattle, banning only specified risk materials -- such as tongues, brains, part of the intestines and vertebrae marrow that are known to have the greatest risk of transmitting mad cow disease to humans -- from cattle older than 30 months.

Conservative right-wing protesters, including war veterans, shout slogans at a rally supporting the government's deal for U.S. beef import and its free trade agreement (FTA) deal with the U.S., in Seoul June 10, 2008. (Xinhua/Reuters Photo)

President Lee has repeatedly stated that South Korea will only import U.S. beef from cattle younger than 30 months old. He asked for Washington's cooperation in his first-ever telephone talk with U.S. President George W. Bush over the weekend.

Critics say the beef pact cannot protect South Koreans from the disease. Civic groups have suggested that Seoul impose stricter guidelines to ban meat from cattle older than 20 months, as Japan does. Younger cattle are generally less prone to contracting the brain-wasting illness.

U.S. legislators have warned they will not ratify the free trade agreement unless Seoul first opens its beef market.

Police set up containers on the streets to block protesters' march before an anti-government rally in the central Seoul June 10, 2008.(Xinhua/Reuters Photo)

(Xinhua News Agency June 11, 2008)