The United States on Thursday voiced doubt that Argentina and Iran's planned "truth commission" would bring to justice those responsible for the deadly 1994 bombing of a Buenos Aires Jewish community center.
Argentine courts have said Iran was behind the attack on the Jewish center, which killed 85 people.
The commission agreement, announced over the weekend but subject to the approval of Argentina's Congress, outlines plans for Argentine officials to interview suspects in Iran rather than in a third country, as originally proposed by Argentina.
State Department spokeswoman Victoria Nuland has said little about the commission, but stressed that Iran had a responsibility to work with Argentine authorities to bring those responsible for the bombing to justice.
"We are skeptical that such a just solution can be found in the arrangement announced," Nuland said on Thursday.
"Iran's record of cooperation with international authorities is profoundly deficient, which underlines the concern that its engagement on this matter be focused on achieving justice promptly," she added in a written response to a question.
Israel and world Jewish groups denounced plans by Argentina and Iran to form a truth commission, which was regarded as a diplomatic victory for Iran as it confronted a U.S.-led effort to isolate Tehran because of its nuclear program.
Western nations fear Iran intends to use the program to produce atomic weapons. Iran denies this, saying its program is solely for peaceful purposes such as generating electricity and producing medical isotopes.
The bombing occurred two years after a group linked to Iran and the Lebanese militant group Hezbollah claimed responsibility for a bomb attack on the Israeli Embassy in the Argentine capital that killed 29. Iran has denied links to either attack.