Supporters of Hugo Chavez will on Thursday hold a rally in honour of the Venezuelan president, who is in Cuba recovering from cancer surgery and will miss a fourth-term inauguration ceremony.
His inauguration has been postponed to an unspecified date. The Supreme Court on Wednesday rejected opposition demands to declare Chavez temporarily absent.
The opposition criticized the Supreme Court ruling that the government could continue to rule in Chavez' absence and that he could be sworn in at a later date.
"Uncertainty has not been dissipated and we have a lying government," said Henrique Capriles Radonski, who lost the presidential election to Chavez in October.
The opposition accuses the government of downplaying Chavez' health problems to secure its grip on power.
Chavez supporters plan to march towards the Miraflores presidential palace, where party leaders and officials will pay tribute to the president.
Heads of state from Bolivia, Ecuador, Nicaragua and Haiti were expected to attend, as were heads of government from several Caribbean nations.
Meanwhile, the national telecommunications commission Conatel said it had launched proceedings against broadcaster Globovision, which is critical of the government, over its coverage of the inauguration dispute.
Globovision vice-president Maria Fernanda Flores said the proceedings were an "attack against the freedom of expression."