A total of five gathering points have been set for the rally to protest the Trans-Pacific Partnership Agreement (TPPA) tomorrow.
They are Maju Junction, Masjid Negara, Masjid Jamek, Masjid India and Sogo.
Protesters are told to assemble at the gathering points starting at 2pm, before converging at Dataran Merdeka.
Parti Sosialis Malaysia (PSM) announced that the party - together with Parti Amanah Negara (Amanah) and a number of other NGOs - will be gathering at Maju Junction, where Amanah president Mohamad Sabu is expected to lead the crowd.
The rally is a last-ditch effort to stop the TPPA, which is expected to be voted on in Parliament at the end of this month.
The protest will also see a gathering of disparate groups that have traditionally been opposed to each other.
It is unclear how big of a turnout the rally will receive, but organisers have estimated it to be in the "thousands" .
Meanwhile, Perkasa pledged that the crowd it plans to mobilise will number in at four figures.
"There will be at least 1,000 from Perkasa," said the NGO's chief, Ibrahim Ali.
Meanwhile, Dang Wangi district police chief Zainol Samah confirmed that police have received a notice about the rally from its organisers.
He noted that the rally organisers have agreed to converge at Padang Merbok if they fail to secure permission from DBKL to gather at the original venue, Dataran Merdeka.
"Police urge rally participants not to gather at Dataran Merdeka and proceed to Padang Merbok.
"The police will not hesitate in taking stern action if there is any breach of law, and participants are required to abide by the police's advice," he said.
He added that police will help to maintain the peace and prevent any groups from creating trouble.
In a related development, Zainol said police have arrested six men who had vandalised public property by spray painting an anarchist symbol ahead of the rally.
"Police are questioning them and identifying those involved to track down the remaining members of the group who are still free," he said.
