Iran is "ready to examine" US information behind accusations that Tehran plotted to kill the Saudi ambassador to Washington, Foreign Minister Ali Akbar Salehi said Monday.
"We are ready to examine with deliberation any issue, even if it was fabricated. We have asked America to provide us with information of this scenario," Salehi was quoted as saying by the official IRNA news agency.
Iran has sent a letter to US authorities via the Swiss embassy in Tehran asking for information about an Iranian-American in US custody accused of being at the centre of the alleged plot. It also demanded consular access to the suspect.
Iranian officials and leaders have fiercely denied any involvement in the alleged plot, calling it an attempt by Washington to divert attention from domestic economic woes and foreign policy failures in the Middle East.
The denials have become louder as the United States is trying to further isolate Iran, which is already subject to severe economic sanctions over its controversial nuclear programme.
Iran's supreme leader, Ayatollah Ali Khamenei, warned Sunday that "any inappropriate action -- whether political or security-related -- will meet with the Iranian people's decisive response."
The head of the US Senate Intelligence Committee, Dianne Feinstein, said after that warning that the United States and an "increasingly hostile" Iran were on a "collision course."
The two countries broke off diplomatic ties three decades ago, ever since Islamic students in Tehran took US diplomats hostage following Iran's revolution. Today they are arch-foes battling for influence over the Middle East.
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He denied repeated US accusations that Tehran sponsored terrorism, and said, according to the state television website: "The Islamic Republic of Iran is a country committed to its international obligations, and it will defend its rights under international law."
Senior Iranian lawmaker Alaeddin Borujerdi, chairman of a parliamentary foreign affairs committee, was quoted by the Fars news agency as saying: "If the Americans are honest about the claims regarding the assassination of the Saudi ambassador, they should forward their evidence to Tehran ... through the Swiss embassy."
The United States says its chief suspect, an Iranian used-car salesman who is a naturalised US citizen living in Texas, Manssor Arbabsiar, confessed to acting as an agent for his cousin, whom he described as a high-ranking official in the Quds Force that forms part of Iran's Revolutionary Guards.
Arbabsiar is alleged to have tried to contract a Mexican drug cartel to assassinate the Saudi ambassador, Adel al-Jubeir, possibly through the bombing of a Washington restaurant.
But, according to US officials, Arbabsiar's contact in the cartel was a paid FBI informant who raised the alert.
The US Justice Department's criminal complaint against Arbabsiar alleged that high-ranking Quds Force officials transferred nearly $100,000 to the informant's bank account as down payment for the $1.5-million-dollar hit.
The man US officials say was Arbabsiar's face-to-face contact in the Quds Force, Gholam Shakuri, alleged to be an aide to Arbabsiar's cousin, was also charged with trying to murder a foreign dignitary with a "weapon of mass destruction."
However Shakuri was not in US custody, and was believed to be in Iran.
US President Barack Obama has vowed Iran will "pay a price" for the alleged assassination plan.
Saudi Arabia has also said it will make "a suitable response" and requested the matter be brought before the UN Security Council.