After a year of negotiations and an eleventh- hour concession by Seoul, South Korea and the United States on Saturday signed a free trade agreement (FTA) that removes nearly all tariffs on commodities, except rice according to DPA. US Trade Representative Susan C Schwab and South Korean Trade Minister Kim Hyun-chong signed the deal at Washington's oldest congressional office building - a hint that the pact still needs approval from both countries' legislatures. For the US, it is the largest trade treaty since the 1994 North American Free Trade Agreement (NAFTA), which Washington signed with Mexico and Canada. Washington and Seoul were under pressure to wrap up the deal before the midnight Saturday expiration of US President George W Bush's "fast-track" authority for trade pacts, which limits Congress to a yes or no vote without amendments. Schwab called the deal a milestone in half a century of US-South Korean ties and said it would boost prosperity in both nations. Seoul made last-minute concessions Friday by agreeing to tougher labour and environmental standards demanded by the new Democratic-led US Congress. South Korean Prime Minister Han Duck-soo said Friday that the Democratic-led Congress might reject the deal without changes to the pact negotiated by Bush's Republican administration. "We have a lot of work ahead of us to educate lawmakers" in both countries to the "enormous benefits of the agreement," Schwab said in remarks prepared for the signing ceremony. The deal discards almost 90 per cent of each side's tariffs on industrial goods, while all remaining tariffs are to be phased out over three to 15 years.