People demanding President Yoon Suk Yeol's ouster stage a rally near the presidential residence in Seoul, Sunday. Yonhap

As the deadline to execute a warrant to detain President Yoon Suk Yeol fast approaches, it remains uncertain how investigators will proceed with his detention amid strong resistance from his security service and supporters, according to political watchers, Sunday.

They say the Corruption Investigation Office for High-ranking Officials (CIO) and the police may make a second attempt to execute the warrant before the Monday deadline expires.

With the warrant, investigators can detain Yoon for questioning for up to 48 hours. If they want to arrest him, they have to ask the court to issue an arrest warrant. Yoon faces charges of leading an insurrection and abusing power regarding his Dec. 3 martial law decree that was later lifted by the National Assembly.

On Friday, investigators called off the warrant execution after hours of confrontation with the Presidential Security Service (PSS) and Yoon's supporters who blocked their efforts.

The joint investigation team of the CIO, the police and the defense ministry's investigation unit summoned PSS chief Park Chong-jun, who denied entry to investigators, for alleged obstruction of justice. However, Park defied the request and the police again requested Park and his deputy Kim Seong-hoon to appear for questioning on Tuesday.

Yoon's lawyer Yun Gap-geun said Sunday that he will file a complaint with the prosecution this week seeking an investigation into some 150 law enforcement officials, including CIO chief Oh Dong-woon, for attempting to execute a warrant to detain Yoon.

"Disobeying security orders is a serious matter that undermines the foundation of the presidential security system essential to national security," Yun said. "We aim to hold those who committed illegal acts accountable under relevant laws."

Yoon's legal team has repeatedly argued that the warrant issued by the court is illegal and invalid, pledging to take further legal action against it.

It filed an injunction with the Constitutional Court to suspend the warrant, as well as a separate objection to the Seoul Western District Court over the order. However, the Seoul Western District Court on Sunday dismissed Yoon's objection to executing the warrant to detain him.

After the arrest failed, the CIO asked Acting President Choi Sang-mok to get the PSS to cooperate in executing the detention warrant on charges of insurrection and abuse of power.

If Choi orders the PSS to cooperate, chances of Yoon being arrested before the Jan. 6 deadline will increase. But the acting president is confronting challenges including a severe backlash from the ruling People Power Party (PPP) for appointing two of the three Constitutional Court justices.

On the other hand, the PSS has said that the CIO "unlawfully intruded" into the presidential residence and said it would hold the investigators legally accountable for their actions.

The PSS chief said Sunday it would be dereliction of duty to cooperate in the execution of the detention warrant.

"We exist solely for the absolute safety of the president. Cooperating with the execution of a warrant against the president means giving up protecting the president," Park said in a statement.

If investigators fail to detain Yoon before the deadline, they could seek a new warrant that would allow them to detain him longer than the 48 hours allowed under the current court order.

Oh Dong-woon, chief of the Corruption Investigation Office for High-ranking Officials, is walking to the Government Complex Gwacheon, Sunday. Yonhap

Meanwhile, rival parties butted heads over the CIO's failed attempt to detain Yoon.

Citing the safety of citizens, police, military and security personnel, the ruling party requested the CIO to suspend its attempt to execute the warrant. It also demanded the CIO to transfer the martial law case surrounding Yoon to the police, saying the corruption investigation organ lacks legal authority to investigate the case.

The main opposition Democratic Party of Korea (DPK) strongly criticized the presidential security, which blocked the warrant execution. It also pressured the CIO to immediately execute the warrant again as soon as possible.

"We issue a stern warning to the PSS. Blocking the warrant execution amounts to an act of rebellion. Oh Dong-woon, the chief of CIO, must not evade his responsibility and promptly execute the warrant to detain Yoon," said Rep. Park Chan-dae, floor leader of the DPK.

Meanwhile, the Constitutional Court said it would expedite the impeachment trial due to the seriousness of the case. It plans to hold five court hearings for Yoon's impeachment trial until early February – on Jan. 14, 16, 21, 23 and Feb. 4.

Yoon's lawyer said the embattled president will testify at his impeachment trial regarding his short-lived declaration of martial law.