Most congressional Democrats oppose the the pact and contend it treats U.S. car manufacturers unfairly.
U.S. Trade Representative Ron Kirk recently said the agreement would not be enforced until South Korea opened its doors to U.S. automakers.
The recently inked trade deal between the EU and South Korea eliminates tariffs on cars in 3 to 5 years.
Under the U.S.-- Korea deal, Korea eliminates auto tariffs immediately. The U.S. eliminates them within 3 years.