TEHRAN (Reuters) - Iran said on Monday it would examine "seriously and patiently" U.S. allegations it planned to assassinate a Saudi ambassador and called on Washington to send evidence of the plot it has dismissed as baseless propaganda.
"We are prepared to examine any issue, even if fabricated, seriously and patiently, and we have called on America to submit to us any information in regard to this scenario," Foreign Minister Ali Akbar Salehi was quoted as saying by the official IRNA news agency.
U.S. authorities said last week they had foiled a plot to kill Saudi's ambassador to Washington, Adel al-Jubeir, and had arrested an Iranian-U.S. joint national -- news that raised tensions between Tehran, its Arab neighbors and the West.
President Barack Obama said the foiled plot should lead to tighter sanctions against Iran -- already under several rounds of U.N. sanctions over its nuclear program -- and repeated that all options are on the table to deal with the Islamic republic, a tacit threat of possible military action.
U.N. Secretary-General Ban Ki-moon said on Monday he had passed correspondence about the U.S. suspicions of Iran's involvement in the alleged plot to the U.N. Security Council.
Tehran says Washington fabricated the plot to divert attention from its own economic problems and increase pressure on Iran, which it has long considered a supporter of "terrorist" groups with nuclear weapons ambitions.
Supreme Leader Ayatollah Ali Khamenei has warned the West Iran will counter any "inappropriate measure" taken against it and said he had no fear of military or sanctions threats.
"Despite the high military, security, propaganda and sanctions pressure, the Islamic Republic is proud not to back down even an iota during the past 32 years," he said in a televised speech during a tour of Kermanshah province.
"The Iranian nation and its officials will not yield to the enemies' blackmailing and pressure."
The plot furor appears to have killed any chance of a rapid return to talks between Tehran and world powers concerned about its nuclear program, but Salehi said Iran continued to make strides in the technology it says is for purely peaceful ends.
Salehi conceded Iran had initially feared the assassination of a nuclear scientist in Tehran last November -- which it blamed on Israel -- had dealt a severe blow to a key part of its atomic work.
"When (Majid) Shahriyari was martyred we were worried because he was the only person who knew about this professional field (enriching uranium to 20 percent purity)," he said.
"But after our trip to (the nuclear plant in the city of) Isfahan, I understood that the graceful martyr had trained about 20 people in his workshops. Right now we have several thousand nuclear engineers and there is almost nothing in the nuclear issue that we want to achieve but cannot."
Iran's announcement last year that it had escalated uranium enrichment from the low level needed for electricity production to 20 percent, alarmed many countries that feared it was a key step toward making material potent enough for a nuclear bomb.
Tehran says the fuel is needed to make isotopes for cancer treatment and previous nuclear talks focused on a deal to deliver ready-made fuel for its medical reactor in exchange for some of Iran's stock of low-enriched uranium.
Salehi said in January -- ahead of the last round of nuclear talks that then stalled -- that such a fuel swap deal was becoming less relevant as Iran would be able to produce its own fuel plates for the reactor in the first half of the Iranian year, which began in March.
With that deadline already passed, Salehi said on Monday Iran would be producing the medical reactor fuel within the next four to five months. He said Iran had produced almost 70 kg (150 lb) of 20 percent enriched uranium, up from an estimated 40 kg in January.
Writing by Robin Pomeroy; editing by Philippa Fletcher