Argentine lawmakers approved a deal struck with Iran to set up a "truth commission" to investigate a deadly 1994 bombing of a Jewish center that killed 85 people and wounded 300.
Argentina, home to Latin America's largest Jewish community, says Iran was behind the attack.
The agreement reached in the wee hours of Thursday has been sharply criticized by Israel, Argentina's Jewish community and opposition politicians.
The pro-government bloc backing President Cristina Kirchner in the Chamber of Deputies secured passage with 131 votes to 113 opposition votes against. The Senate gave its green light last week.
Argentina has long suspected Iran of being behind the 1994 bombing of the AMIA Jewish charities building in Buenos Aires, which came two years after a similar attack on the Israeli embassy. Tehran has denied any involvement.
The deal sets up an independent "truth commission" to probe the bombing, which the Argentine government says will pave the way for eight Iranian suspects to be questioned by an Argentine judge.
The eight include Iran's Defense Minister Ahmad Vahidi, former president Akbar Hashemi Rafsanjani and ex-foreign minister Ali Akbar Velayati, who have had international arrests warrants out against them since 2006.
Iran, however, has insisted none of the suspects will be questioned.
AMIA president Guillermo Borger said the organization will file suit with the Argentine Supreme Court to have the accord with Iran struck down. Rather than get to the bottom of the attack, it will lead to the investigation being shelved, he argued.
Israel also expressed disappointment with the Argentine lawmakers' vote.
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"Past experience has shown that agreements with the government of Iran are not kept, and fail to change the line of Tehran," the Israeli Foreign Ministry said.
"Unfortunately, the current agreement will also fail to achieve what has been and still is the only goal: bringing to justice those responsible for the terror attacks in Buenos Aires and punishing them for their deeds."
In announcing the accord on January 27, Kirchner said the commission would consist of five independent judges -- none of whom can come from either Iran or Argentina.
At the time, she called the agreement "historic," saying "it guarantees the right to due process of law, a fundamental principle of international criminal law."
But it has been sharply criticized by Israel and Argentina's 300,000-strong Jewish community, which has called on authorities to continue to try to apprehend the suspects and put them on trial.
Hundreds of community members gathered in front of the Argentine Congress in protest, holding up signs that read "No."
"What kind of cooperation can we have with (Iran)? The bombing is being debated with the Iranian government, which ordered it," opposition legislator Ricardo Gil Lavedra said during debate on the bill.
Israel's foreign ministry has protested the deal, while Washington has cast doubt that any solution will emerge from it.
The Iranian parliament has yet to approve the agreement.
The July 18, 1994 bombing occurred when a van loaded with explosives blew up outside the Argentine Jewish Mutual Aid Association (AMIA), leveling the seven-floor building housing the charities federation.
An attack on the Israeli embassy in Buenos Aires two years earlier killed 29 people and wounded 200.