The free trade agreement (FTA) clinched with only minutes to spare in Seoul is not assured passage in Congress, which is controlled by the Democratic Party.

In fact, some lawmakers say they will even block consideration of the FTA unless Seoul moves to end its ban on US beef imposed due to concerns about mad cow disease.

The exclusion of rice -- considered a sensitive commodity in Korea -- may also make approval harder, say analysts. And the phasing out of US tariffs on Korean-made pickup trucks could prompt opposition in Washington among critics who argue the South Korean auto industry benefits from unfair advantages in its home market.

Deputy US Trade Representative Karan Bhatia said the deal, the biggest since the North American Free Trade Agreement, is "a very strong FTA" that opens up financial services and makes 95 percent of bilateral trade in consumer and industrial products duty free within three years.

Bhatia said the agreement includes "provisions to level the playing field in the automotive area," and "is also a very strong agriculture agreement."

Nonetheless, the announcement got only a lukewarm response from lawmakers.

"I have mixed feelings," said Republican Senator Chuck Grassley.

Grassley said although the trade pact is "commercially significant," he added: "I'm disappointed that rice was excluded from the agreement. On principle, I oppose taking agricultural products off the table in trade negotiations. It just facilitates the continuation of protectionism."

The Iowa senator noted that the agreement "is dead on arrival until the beef issue gets resolved," he said.

While the ban on beef is not officially part of the free-trade agreement (FTA), both sides acknowledge that US lawmakers would reject any deal unless the issue is resolved.

"I don't think the Congress will approve an FTA with Korea without the full reopening of the Korean beef market," Bhatia told reporters on a conference call from Seoul. "We have made that very clear to Korea and they understand that."

Before a 2003 import ban, South Korea bought 850 million dollars' worth of US beef a year. Seoul last year agreed to accept US boneless beef but rejected three shipments after discovering tiny bone fragments.

Seoul did agree to phase out its 40 percent tariff on beef over 15 years. Tariffs on pork will go over 10 years.

On the ban, Korean officials said in Seoul they promised to "positively consider" US demands on beef after the International Organization for Animal Health reviews mad cow risks in the US.