Iran's Supreme Leader Ayatollah Ali Khamenei waves to his supporters before starting his speech in the province of Kermanshah, west of Tehran October 15, 2011.[Photo/Agencies]

TEHRAN - Supreme Leader of the Islamic Republic Ayatollah Seyyed Ali Khamenei said Saturday that the alleged Iranian involvement in a plot of assassinating the Saudi ambassador to the US is "absurd" and "meaningless", the semi- official Mehr news agency reported.

On Tuesday, the US Justice Department alleged that two men, Manssor Arbabsayar, a 56-year-old US citizen holding both the Iranian and US passports, and Gholam Shakuri, an Iranian citizen, were charged with sponsoring and promoting terrorist activities abroad, including a plot to kill Saudi Ambassador to Washington Adel Al-Jubeir.

These "absurd" and "meaningless" charges will further lead to US global isolation, said Khamenei.

The US claim is a plot and a propagandistic show which will end in isolating itself, he said while addressing a crowd in the city of Gilan-e Gharb in Iran's western province of Kermanshah.

They tried to find an excuse to mount a propaganda campaign to present Iran as the supporter of terrorism through leveling accusations against several Iranians, he said, adding but their plot fell flat like their other actions, he was quoted by Mehr as saying.

During the past days, Iranian authorities have dismissed the US claim as fabrication but US high ranking officials insisted on the authenticity of their evidences and said that they will work with their allies to pressure Iran.

US President Barack Obama said on Thursday that there would be "no dispute" over the US claim after they analyzed the facts.

He called the plot "not just a dangerous escalation," but "part of a pattern of dangerous and reckless behavior by the Iranian government," vowing to seek the "toughest sanctions" against Iran.

On Thursday, US State Department spokeswoman Victoria Nuland said the United States had "direct contact" with Iran over the alleged involvement of the Iranian government in a plot of assassination.

On Friday, the Iranian authorities denied that the United States had "direct contact" with Iran over the alleged involvement of the Iranian government in the assassination plot.

The press officer of Iran's Representative Office to the United Nations, Alireza Miryousofi, told Mehr on Friday that "No direct talks have been held between the two countries" over the alleged plot.

Later on Friday, the US State Department dismissed Iran's denial on direct contact between the two countries over the alleged assassination plot.

"I will again confirm that we did meet with the Iranians. It was two days ago," State Department spokeswoman Victoria Nuland said.

"They know that very well, and any efforts on their part to deny it speaks again to how truthful they are about any of these sorts of matters," she said.

Nuland said the US had made it clear to Iran that the plot violated the US and international law, and Iran would be held accountable.

David Cohen, US Under Secretary of Treasury for Terrorism and Financial Intelligence, said Friday at a hearing held by the House Foreign Affairs Committee that the US is seeking multilateral support in an effort to impose additional sanctions on Iran's central bank.

"Yes, we are engaging in an effort to develop the multilateral support that would be, I think, critically important in having an action against the CBI (Central Bank of Iran) really be effective, " said Cohen.

"Further US action against the CBI, if it attained multilateral support, could further isolate the CBI, with a potentially powerful impact on Iran," he warned.

Cohen said the US has imposed comprehensive sanctions on Iran for almost two decades, including sanctions on the Central Bank of Iran.

"So there is no US financial institution that has any dealings with the CBI, including the Federal Reserve," said Cohen, adding that the CBI is "essentially and completely cut off" from the US.