Pakistan approached the United Nations to probe the assassination of Bhutto as it wanted to uncover the conspiracy to "balkanise" the country, Zardari told the three-member UN Commission of Inquiry probing the facts and circumstances of his wife's assassination, in Islamabad on Thursday.
"We approached the UN because firstly we wanted transparent and above-board investigations so that there are no accusations of bias," he said.
"We also wanted to unearth any conspiracy to balkanise Pakistan and let the world know how a democratic leader heroically laid down her life to foil the designs against the country and thereby to honour her internationally," he said.
Zardari said the conspirators "planned to postpone (the February 2008) elections indefinitely and provoke the Pakistan People's Party into taking to the streets...to hasten the process of balkanisation."
However, the PPP decided to seek revenge in a different way as its new chairman Bilawal Bhutto Zardari declared "democracy is the best revenge," he said.
"We have also carried out our own investigations and the findings will be made available to the UN investigators," Zardari said.
He said the commission was faced with a "challenging and onerous" task.
Bhutto's three children Bilawal, Bakhtwar and Aseefa were present during Zardari's meeting with the commission, which on Friday began its first visit to the country.
The commission will be accorded immunities for an independent inquiry, including unhindered access to all relevant sources of information, presidential spokesman Farhatullah Babar said.
Earlier, the commission was briefed by a team of the interior ministry on their investigation into Bhutto's killing.
The commission headed by Ambassador Heraldo Munoz of Chile also met Interior Minister Rehman Malik, Foreign Minister Shah Mahmood Qureshi and Minister of State for Law Muhammad Afzal Sindhu.
The commission is "committed to assist Pakistan by doing its utmost to determine the facts and circumstances of (Bhutto's) death," said a statement issued by the UN.
The commission's mandate was decided by the UN in consultation with the Pakistan government.
The UN has made it clear that the panel's mandate does not include the conduct of a criminal investigation.
Bhutto was killed in a gun and bomb attack shortly after addressing an election rally in Rawalpindi in December 2007.