The move came hours after the United Nations General Assembly adopted a resolution calling for the "immediate and unconditional" return of Manuel Zelaya to the Honduran presidency, two days after he was forced into exile in Costa Rica.
Show of support
The resolution backed condemnations by the OAS and other regional groups of what Zelaya described as "the barbarity that a small group of usurpers sought to inflict upon our country".
Christina Fernandez, Argentina's president, and Insulza are set to accompany Zelaya during his planned return to Honduras on Thursday in a show of support.
The adoption of the General Assembly resolution came as supporters of both Zelaya and his interim replacement demonstrated in the country's largest cities.
Al Jazeera's Monica Villamizar, reporting from San Pedro Sula, Honduras' commercial capital, said the protests are evidence that the coup has left the country deeply polarised.
"The police said for the moment that they have avoided a full-scale confrontation, but tensions are clearly mounting and anti-riot troops have cordoned off government buildings and shielded supporters of the military-installed government," she said.
"Zelaya supporters have called for a general strike until he returns. Many said he was a president who was helping the poor.
"But only blocks away, others said Zelaya was a threat to democracy, too easily influenced by left-wing governments like Venezuela and trying to modify the constitution to remain in power."
Threat of arrest
Roberto Micheletti, who was appointed interim leader by the Honduran congress just hours after the coup, has said he will have Zelaya arrested if he returns to Honduras.
Micheletti, a former parliamentary speaker from the same Liberal party as Zelaya, vowed not to resign as interim president and said only an armed invasion would restore his ousted predecessor.
"No one can make me resign," he said.
"[Zelaya] can no longer return to the presidency of the republic unless a president from another Latin American country comes and imposes him using guns."
"I was appointed by congress, which represents the Honduran people. Nobody can make me resign unless I break the laws of the country," he told the Associated Press news agency.
Micheletti has insisted that Zelaya was not ousted through a coup but through "a completely legal process as set out in our laws", calling the move an "act of democracy".
Zelaya was removed from power as he was about to press ahead with a non-binding referendum on constitutional change on Sunday that congress and the courts had declared illegal, accusing him of trying to change the charter so he could run for a second term in office.
Before the General Assembly's condemnation of the coup, the overthrow of Zelaya was roundly criticised by Latin American countries and the US.
Members of the Bolivarian Alternative for the Americas (Alba), which includes Venezuela and Bolivia, said on Monday that they would withdraw their ambassadors from Honduras.
Barack Obama, the US president, also criticised the coup.
"We believe that the coup was not legal and that President Zelaya remains the democratically elected president there," Obama said.
Mariana Sanchez, Al Jazeera's correspondent in Honduras, said: "Spain and France have recalled their ambassadors. The US has joined its voice of condemnation with the UN.
"Although it has been a bit vague in qualifying what is going on here, Washington has a legal team analysing if this was a coup d'etat or not.
"The countries that border Honduras ... are considering closing their borders … Honduras is becoming a pariah country without any ties.
"The Micheletti government is sending a mission to Washington to explain what they say is a constitutional succession, but Washington has said it will not meet this delegation."
The US has not legally classified the removal of Zelaya as a coup d'etat as it would automatically lead to the suspension of aid to Honduras, an impoverished nation of 7.2 million people.