"The policy of 'maximum pressure' against the Iranian nation is worthless and all Islamic Republic of Iran officials unanimously believe there will be no negotiations with the US at any level," Khamenei said, referring to the US' latest strategy on Iran.
Earlier this month, US officials raised the prospect of direct talks between US President Donald Trump and his Iranian counterpart Hassan Rouhani on the sidelines of the UN General Assembly scheduled for next week.
Secretary of State Mike Pompeo and Treasury Secretary Steven Mnuchin said there would be "no preconditions" for the talks, but Trump later dismissed the remark as an "incorrect statement."
Read more: German government split on Saudi arms ban
Rising tensionsWashington and Tehran have seen relations deteriorate since Trump unilaterally withdrew the US from the Iran nuclear deal. The White House has also deployed warships and bombers to the Persian Gulf after several oil tankers were sabotaged over the summer.
In the latest development between the rivals, the White House on Monday suggested that Iran was behind attacks against oil facilities in Saudi Arabia although Houthi rebels in Yemen had claimed responsibility.
"I'm not looking to get into new conflict, but sometimes you have to," Trump said. "That was a very large attack, and it could be met by an attack many, many times larger."
"Certainly, it would look to most like it was Iran," he added.
Germany, the UK and China have urged caution, saying efforts must be taken to verify who is responsible for the attack before attributing blame.
Read more: Saudi Arabia vs. Iran: From 'twin pillars' to proxy wars
Saudi invites UN to investigateMeanwhile, Saudi Arabia has invited the UN and international experts to "view the situation on the ground and to participate in the investigations."
The attacks significantly disrupted Saudi oil production, triggering a global oil supply slump of more than 5%.
Oil prices surged as soon as markets opened on Monday, with the US, Russia and even Japan saying they are considering tapping into oil reserves.
Read more: Shock and awe, but few surprises as oil prices spike
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ls/stb (AFP, AP)