The National Assembly looks almost certain to miss a legal deadline to handle the government's 2020 budget proposal on Monday amid intensified tensions sparked by the main opposition party's threat to use a filibuster.

Dec. 2 is the legal deadline for the parliament to pass the government's record high 513.5 trillion-won ($435 billion) budget proposal for next year.

But it is highly likely that parliament will miss the deadline for the fifth straight year as partisan conflicts have shown no signs of easing over key contentious reform bills.

The main opposition Liberty Korea Party threatened Friday to launch a filibuster or long speech over 199 bills as the conservative party seeks to block a parliamentary vote on bills on electoral reform and the revamp of state prosecutors.

The so-called prosecution reform bills -- proposals to set up an independent unit to probe corruption by high-ranking officials and give more investigative authority to police -- are expected to be referred to a plenary session Tuesday.

The ruling Democratic Party is considering joining hands with four minor parties to put the stalled parliamentary regular session back on a normal track. The 100-day session will end on Dec. 10.

"Unless the LKP promises to withdraw a filibuster bid and to normalize the parliament, we will handle the government's budget proposal and bills linked to people's lives through cooperation with other opposition parties by the end of the regular session," DP Chairman Lee Hae-chan said at a party meeting.

The government's 2020 budget proposal came as the Korean economy is losing steam on faltering exports and sluggish domestic demand.

A key centerpiece of the spending plan is 24.1 trillion won set aside for research and development to counter the fallout of Japan's export curbs against South Korea. (Yonhap)