A New York court last week ordered Tehran to pay USD 7.5 billion to victims of the September 11, 2001 attacks on the World Trade Center and the Pentagon -- and USD 3 billion to insurers over related claims -- after ruling that Iran had failed to prove that it did not help the bombers.
"This judgement is so ridiculous... More than ever before, it damages the credibility of the US judicial system," state television quoted an Iranian foreign ministry spokesman as saying.
"We also see the US administration as a partner in such verdicts," Ansari said.
Mohammad Javad Larijani, secretary general of Iran's High Council for Human Rights, also criticised the ruling.
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"If they (the United States) want to prosecute anyone over the September 11 incident, it should be their allies in the region who created Al-Qaeda and funded it," he said.
Al-Qaeda claimed responsibility for the 2001 attacks that killed nearly 3,000 people.
He was killed on May 2, 2011 by US special forces in his residence in Abbottabad, Pakistan.
Relations have been tense between regional rivals Iran and Saudi Arabia, who back opposing sides in the Syria and Yemen conflicts.
The Shiite republic and Sunni kingdom severed diplomatic ties in January after Riyadh executed a Saudi Shiite cleric and protesters ransacked the Saudi embassy in Tehran.
The only Al-Qaeda plotter convicted over the 9/11 attacks told American lawyers that members of the Saudi royal family donated millions of dollars to the group in the 1990s.
In July last year, world powers including the US signed a landmark deal with Iran to lift crippling economic sanctions in exchange for Tehran curbing its nuclear programme.