SEOUL, Nov. 2 (Yonhap) -- The floor leader of the ruling Grand National Party (GNP) Wednesday opposed using the Assembly speaker's authority to pass the long-pending free trade deal with the United States on the floor, saying a unilateral passage would cause distrust in party politics.

Since the U.S. Congress endorsed the pact in early October during President Lee Myung-bak's state visit, Korea's rival parties have been deadlocked over the free trade deal with the U.S., with the opposition parties asking for a revision of an investor-state dispute (ISD) settlement provision.

After several rounds of failed negotiations between the GNP and the main opposition Democratic Party (DP), speculations surfaced that the ruling party may ask Speaker Park Hee-tae to send the bill straight to the plenary session, omitting the sub-committee's approval.

GNP floor leader Hwang Woo-yea refuted the possibility of the unilateral passage, saying it could cause backlash against the party amid growing public distrust in politics.

"It is not appropriate to use (the speaker's) authority," Hwang said in a radio interview. "This is not merely an internal matter; the world is watching us now."

Mentioning the DP's recent efforts to form a liberal alliance with splinter opposition parties, which are strongly opposed to the FTA, Hwang urged the rival parties to set aside partisan politics over the trade pact for national interests.

Tensions are rising over physical brawls at the National Assembly over the contentious bill. Floor leaders of the GNP and the DP earlier this week reached a tentative agreement to prepare additional safeguards to protect local industries to pave the way for the accord's ratification.

Despite partial agreement, they failed to agree on the ISD, a provision that allows foreign investors to bring trade dispute claims directly against the government of the co-signatory before an international panel of arbitrators.

The DP has demanded the ISD be removed from the accord, arguing the provision would limit Seoul's policies on American investors. The government says the DP's demand is not acceptable and other FTAs currently in place also include such clauses.

DP floor leader Kim Jin-pyo reaffirmed his stance against the ruling party's attempt to ram through the bill without revising the controversial provision.

"If the S. Korea-U.S. FTA goes into effect next year without revising the ISD, the U.S. will never change the clause," Kim said in a party meeting.

The ruling party has a solid majority to approve a bill but has been reluctant to drive the pact through parliament and risk scuffles at the National Assembly.