The National Assembly will hold a plenary meeting this week to vote on a bill to permit a million voters to propose a constitutional revision, as the ongoing extra session is set to end in mid-May, lawmakers said Monday.

In March, nearly 150 ruling and opposition lawmakers submitted to the parliament a motion to amend a constitutional clause in a bid to allow voters to propose a constitutional revision, along with a majority of lawmakers and the president.

Rival political parties agreed to hold a plenary meeting Friday to handle the bill, according to Rep. Lee In-young, floor leader of the ruling Democratic Party (DP).

The main opposition United Future Party (UFP) agreed to open the session but decided to boycott the meeting and vote, party officials said.

A parliamentary vote is highly expected to fall through due to a lack of quorum. The passage of a constitutional revision requires approval by at least two-thirds of lawmakers or 194 votes in the current 290-member assembly.

The UFP and its sister party Future Korea Party hold a combined 112 seats.

A motion to introduce people's initiative should be put to vote within 60 days after its submission to the National Assembly.

In May 2018, President Moon Jae-in's proposal for a constitutional revision was scuttled as opposition parties boycotted a parliamentary vote to pass the controversial motion.

The 21st National Assembly will set sail on May 30 after new 300 lawmakers were picked in the April 15 general elections.

The DP and the UFP will hold party elections to pick new floor leaders Thursday and Friday, respectively. (Yonhap)