SEOUL (AFP) - Tensions were high Wednesday in South Korea's parliament after talks on ending an Opposition sit-in broke down. About 150 security guards blockaded the parliament on the orders of Speaker Kim Hyong-O. Scores of riot police were also on standby outside. However, dozens of Opposition legislators, helped by more than 200 aides, continued their seizure of parliament. "Most Opposition legislators are inside the main hall for a plenary session after locking up all but one door with iron chains," a spokesman for the office of parliamentary staff told AFP. The ruling conservative Grand National Party (GNP) has asked the speaker to take immediate action and end the sit-in for a final vote, after talks with the main opposition Democratic Party (DP) broke down. Party leaders had agreed on settling about 70 bills but the DP rejected the GNP's proposal to postpone until February the ratification of two contentious bills - a free-trade pact with the United States and legislation to allow media cross-ownership. Clashes involving sledgehammers and fire extinguishers broke out on December 18 when the GNP began procedures to ratify the free trade agreement with the United States. Last Friday, Opposition lawmakers barricaded themselves inside the main parliamentary chamber to thwart approval of the agreement and other legislation. The GNP has 172 seats in the 299-member legislature compared with the DP's 83. The ruling party had insisted that the free trade pact, signed by Seoul and Washington last year but awaiting ratification by both legislatures, should be approved before the end of this year. It sees the pact as necessary to stimulate the slowing economy and believes that approval by Seoul will encourage the US Congress to move faster. The Opposition says South Korea should not ratify it until the US Congress also moves to do so. Business groups want early ratification, but Korean farmers are demanding more measures to protect them against cheaper imports. For the United States, the deal with South Korea would be its biggest since the North American Free Trade Agreement in 1994.