As a deadline for official reviews on the budget by a parliamentary committee passed Friday, rival parties are reviewing the budget proposal through unofficial, closed-door consultation.

Earlier in the day, National Assembly Speaker Moon Hee-sang met with the floor leaders of the ruling Democratic Party and two opposition parties to discuss the schedule for a plenary session.

At the morning session, they failed to reach a compromise with the main opposition Liberty Korea Party and the minor opposition Bareunmirae Party asking for the session to be delayed.

Moon said that if rival parties fail to reach an agreement on the issue by 2 p.m., he plans to put the proposal up for vote later in the day.

"If they fail to reach the agreement, (I will) send the bill to the floor and let the government explain its stance about the proposal," Moon said in a statement.

He also said that if rival parties submit a revised budget bill, he will put it up for vote after adjourning the session.

"As parliamentary speaker, if I do not take any action and watch the three parties' discussions, that would be a shameful act to the people and is not a duty for them," he said.

Rival parties are at loggerheads over an expected 4 trillion-won shortfall in tax revenue and budget set aside for inter-Korean projects and job creation.

The government said that it expects the shortfall due to a series of tax cuts, including a 1.1 trillion-won deficit resulting from a temporary reduction in fuel taxes.

Opposition parties called on the government to devise ways to fill the shortfall, while urging the state to set up its own plan to cut fiscal spending.

Since 2014, the National Assembly has passed a legal deadline for the budget passage every year except that year.

But excluding last year, when a revised budget proposal was passed on Dec. 6, there have been no cases of the budget being passed days after the deadline.

The National Assembly's 100-day regular session ends on Dec. 9.