The Iraqi parliamentary has been heatedly debating over the past two days on a proposed US-Iraq security pact that would allow American forces to stay in Iraq for three more years.

The parliament has completed a second reading of the proposal -- the last step prior to the opening of debate on the security pact ahead of a vote scheduled for Monday.

Lawmakers loyal to Shiite opposition leader Muqtada al-Sadr sought to disrupt Thursday's reading as they did the previous day, and scuffled with the security guards of Iraq's foreign minister and the speaker of the legislature and his two deputies.

The turmoil followed the announcement by two other political factions in the 275-seat legislature that they would oppose the security pact that the Cabinet approved last week.

Iraqi Prime Minister Nouri al-Maliki said the alternative to the security pact - a renewal or an extension of the UN mandate providing legal cover for US forces in Iraq - would compromise Iraq's sovereignty.

"The danger of an extension is the removal of Iraq sovereignty, and facing the same problem again, which will drive us back to searching for another agreement with the Americans."

Maliki assured Iraqis that the timeline for the withdrawal of US forces under the agreement -- out of Iraqi cities by June 30, 2009, and the entire country by the end of 2011 -- is not negotiable and could even be moved up.