Iran confirmed to Argentina on Saturday that it would cooperate to probe the 1994 bombing of a Buenos Aires Jewish center after charges that Tehran ordered the attack, diplomats said.
The van bombing of the building of he Argentine Jewish Charities Federation, or AMIA, left 85 people dead and 300 others injured in the worst attack of its kind ever to strike the South American country.
Iranian Foreign Minister Mohammad Javad Zarif, closing a week of hectic diplomacy at the United Nations that included breakthrough contact with the United States, held talks on the bombing with his Argentine counterpart Hector Timmerman.
"Iranian authorities confirmed that the relevant authorities have approved the agreement," an Argentine diplomat told AFP.
But the deal, which follows talks between foreign ministers a year ago, will not come into force until a formal exchange of documents, she said.
The two sides have still not resolved two key issues, including the naming of a investigatory commission, whose five members will be neither Argentine nor Iranian.
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There has also been no agreement on a date for Argentine investigators to travel to Iran to interview suspects.
Argentina charges that Hezbollah, the Lebanese Shiite movement, carried out the attack under orders from Iran. Tehran's clerical regime denies the charges.
Since 2006, Argentine courts have demanded the extradition of eight Iranians, including former president Akbar Hashemi Rafsanjani, former defense minister Ahmad Vahidi and Mohsen Rabbani, Iran's former cultural attache in Buenos Aires.
The talks at the United Nations come as Western countries voice hope for change in Iran's new president Hassan Rouhani, a self-styled moderate.
Rouhani has vowed to move quickly to clear up doubts on Iran's nuclear program and held a historic phone conversation Friday with US President Barack Obama.
In a speech before the UN General Assembly, Argentine President Cristina Kirchner said she had "expectations of change" in her country's relationship with Iran.
But she warned the Islamic republic not to confuse "patience with naivete or stupidity," and urged Tehran to move ahead on the sticking points of the bombing investigation agreement.
Leaders of Argentina's Jewish community, which at 300,000 people is the largest in Latin America, have criticized the accord.