Kim Jong-nam was murdered on February 13 at the Kuala Lumpur International Airport by VX nerve agent, classified by the United Nations as a weapon of mass destruction.
Malaysian authorities on Saturday said an arrest warrant for a North Korean diplomat wanted for questioning over the murder of Kim Jong-nam would be issued if he does not voluntarily cooperate with the police.
"Reasonable" time will be given for the diplomat to come forward before police take further action, said Abdul Samah Mat, the police chief for Selangor state.
Malaysian officials on Wednesday said that 44-year-old Hyon Kwang Song, a second secretary at the North Korean embassy in Kuala Lumpur, was wanted for questioning over the death of the estranged half-brother of North Korean leader Kim Jong-un.
Samah said if the person concerned did not cooperate, police would issue a notice under Malaysian law, "compelling" them to appear before the investigation team.
"And if he failed to turn up upon given this notice, then we will go to the next step by getting a warrant of arrest from the court," he told reporters.
Kim Jong-nam was assaulted by two women who, according to Malaysian police, rubbed VX nerve agent on his face at Kuala Lumpur International Airport.
Eight North Koreans are wanted in connection with the case, including the diplomat.
Malaysian police have detained one North Korean, while four are believed to have fled to North Korea; two others are still in Malaysia.
Two women — an Indonesian and a Vietnamese — have also been detained.
Police said on Friday that one of them had suffered from the effects of VX poisoning and had been vomiting.
South Korean and US officials said they believed North Korean agents assassinated Kim Jong-nam, who had been living under China's protection.
North Korea denies that the dead man is Kim Jong-nam and has demanded the release of people detained in the case.