Major parties failed Monday to narrow their differences over a constitutional amendment and other disputed motions, triggering the cancellation of a floor session and extending a parliamentary gridlock.

The floor leaders of the ruling Democratic Party, main opposition Liberty Korea Party, Bareunmirae Party and Parliamentary Group for Peace and Justice held three separate meetings, including a luncheon, but could not reach a compromise.

The failure led to the cancellation of a parliamentary plenary session, in which Prime Minister Lee Nak-yon was set to deliver a speech on the government's proposal for an extra budget worth 3.9 trillion won ($3.7 billion).

During their meetings, the floor leaders clashed over how to retool the decades-old Constitution, but they only confirmed their differences on a set of related issues, such as revamping the state governance structure.

Another sticking point was the proposed revision to the Broadcast Act, which calls for electing the chief of a public broadcaster with approval from two thirds of the 13 board members -- seven recommended by the ruling party and six by the opposition bloc.

The opposition parties argue the change should be passed quickly to ensure the political neutrality of public broadcasters, while stressing it was the Democratic Party that first proposed it in 2016. But the ruling party wants further discussions on it.

The LKP and Bareunmirae Party have boycotted major parliamentary sessions, calling for the early passage of the revision.

The failed negotiations are expected to hamper this week's legislative proceedings, such as the parliamentary interpellation of the government scheduled to begin Tuesday.(Yonhap)