The secretary of Iran's Supreme National Security Council accused the United States on Saturday of violating the sovereignty of nations on the "pretext of fighting terrorism" in Iraq and Syria.
"On the pretext of fighting terrorism, the United States want to pursue their unilateral policies and violate the sovereignty of states," Ali Shamkhani said, quoted by the official IRNA news agency.
He said Washington was "trying to divert the eyes of the world from its pivotal role in supporting and equipping the terrorists in Syria in a bid to topple the legitimate regime."
And the speaker of parliament, Ali Larijani, warned the United States that launching strikes against Iran's ally Syria as part of its campaign against the jihadists of the Islamic State group would be "playing with fire."
"The United States is playing with fire in the region and must know that it cannot attack Syria on the pretext of fighting against the Islamic State," he said.
"The United States must know that if it attacks countries in the region... no one will be able to control the region. The fuse will be lit," he warned.
The United States is building an international coalition against the Islamic State and has said it plans air strikes against the jihadists on Syrian territory without the consent of Damascus.
Syria and its ally Russia have warned that any unilateral US military action on Syrian territory would be a violation of its sovereignty.
Shamkhani and Larijani were the latest Iranian officials to criticise US efforts to wage war against the jihadists.
On Thursday, foreign ministry spokeswoman Marzieh Afhkham cast doubt on the "sincerity" of the coalition Washington is seeking to build.
Last week, Foreign Minister Mohammad Javad Zarif accused the United States of not taking the threat from IS militants in Iraq and Syria seriously.
He also charged that US aid had previously helped the jihadists, alluding to support given by Washington to other rebel groups in Syria, some of which has found its way into the hands of IS.
Iran has been Syrian President Bashar al-Assad's main regional ally since the revolt against his rule erupted in March 2011 and has also provided military advisers to the Shiite-led government in Iraq to help it battle the jihadists.
Shamkhani's comments come as France prepares to host a conference on Iraq in Paris on Monday to which Iran has not been invited.
US Secretary of State John Kerry said on Friday his country is opposed to Iran's participation because of its "engagement in Syria and elsewhere".
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