Acting President Han Duck-soo on Thursday vetoed six bills passed in the opposition-controlled National Assembly last month, despite threats from the main opposition Democratic Party of Korea to impeach him if he "crosses the line."

This is the second time in Korea's constitutional history that an acting president has exercised his veto power, with the last instance occurring in 2004.

Prime Minister Han immediately assumed the role of acting president following President Yoon Suk Yeol's impeachment on Saturday by the Assembly, which accused him of insurrection in his botched martial law decree on Dec. 3.

The Cabinet, in an extraordinary meeting held Thursday morning, approved a motion calling for parliament to reconsider the six bills. This includes amendments to the Grain Management Act to require the government to purchase surplus rice in case of unusual price volatility. The bills were sent back to parliament following Han's decision, the Prime Minister's Office said around noon.

The bills will be scrapped if a revote fails to meet the threshold of 200 votes in the 300-member parliament to override the veto. They are likely to be scrapped as the ruling People Power Party, which holds 108 of the 300 seats, is expected to vote against the bills, observers said.

"I have repeatedly contemplated and given much thought (to the bills) as acting president regarding the choice that would best represent the stance of a responsible government in a situation that is serious for the nation," Han said during the Cabinet meeting.

"My heart feels heavy as I request the National Assembly to reconsider the six bills at a critical time when cooperation between the government and political parties is more desperately needed than ever. But the government has to make a decision that reflects its responsibility of prioritizing the spirit of the Constitution and the future of our nation," he added.

On his decision to veto the amendment to the Grain Management Act, Han cited his concern that it could ultimately lead to a drop in the price of rice through the government's excessive involvement in the market.

The bill is a watered-down version of a previous revision to the Grain Management Act, which was vetoed by Yoon in April last year, a month after the opposition-led Assembly passed the bill.

Last year’s version had more detailed conditions, calling for the purchase of excess rice when surplus production exceeds 3-5 percent of demand or when the price of rice falls by 5-8 percent compared to the previous year. The latest version states that a committee and the minister of agriculture, food, and rural affairs have the power to set the standards.

Among the other vetoed bills was a revision to the National Assembly Act, which would abolish the automatic forwarding of the government's budget proposal to a plenary session if bipartisan agreement is not reached by the annual deadline. The current system allows the Cabinet to automatically forward the budget proposal even when it fails to pass through parliamentary standing committees by the annual deadline of Nov. 30.

Recently-elected ruling People Power Party Floor Leader and acting Chair Kweon Seong-dong on Thursday urged the acting president to exercise his veto power over the six bills. He also highlighted the need to introduce a bipartisan bill that would punish lawmakers that voted for Yoon's impeachment motion, if the Constitutional Court decides to reinstate Yoon to power.

"A bipartisan bill is necessary to prevent the Assembly from infinitely pursuing impeachment motions," he explained.

The Democratic Party on Thursday amplified its threat to impeach the acting president if he "crosses the line."

"The ghost of the administration is still alive -- the name of the person who exercises the presidential veto has changed from Yoon Suk Yeol to Han Duck-soo," Democratic Party spokesperson Noh Jong-myeon said in a written statement. "Acting President Han is not the president. Furthermore, he is a suspect in the insurrection case. We warn (Han) that we will drag him down if he is deemed complicit in the insurrection -- do not cross the line."

Noh's statement echoes remarks made Sunday by main opposition leader and Democratic Party of Korea Rep. Lee Jae-myung, who said that the party will not pursue Han's impeachment "for the time being."

Though he did not mention the six contentious bills, Lee indirectly pressured Han to approve two separate proposals for special counsel investigations of the insurrection charges against Yoon and several allegations against first lady Kim Keon Hee, including her alleged involvement in a stock manipulation scandal that unfolded nearly a decade ago.

"(I told Han in a phone call) that refusing either of the two bills could represent political bias," Lee told reporters.

"While many within the party called for Han's impeachment" in connection with the turmoil tied to Yoon's martial law decree, they decided against it, to prevent "confusion in state affairs," he said.