A top adviser to Iranian Supreme Leader Ayatollah Ali Khamenei said Wednesday that any U.S. military action "will be considered" the start of war and a response "will be immediate."

Ali Shamkhani, secretary of Iran's Supreme National Security Council, issued the warning on X, escalating Tehran's rhetoric as President Donald Trump renews pressure on the regime over its nuclear ambitions.

Shamkhani said even a limited U.S. strike would trigger an all-out response, and he also threatened Israel.

"The limited strike is an illusion," Shamkhani wrote. "Any military action by America, from any source and at any level, will be considered the beginning of a war, and the response will be immediate, comprehensive, and unprecedented, directed at the aggressor, at the heart of Tel Aviv, and at all its supporters."

The statement indicated an increasingly confrontational posture of Iran's leadership as Trump ramps up warnings that Tehran must abandon any pursuit of nuclear weapons.

Earlier Wednesday, Trump urged Iran to "come to the table" and negotiate a new nuclear deal, warning that failure to do so would bring severe consequences.

"The next attack will be far worse," Trump wrote on Truth Social, noting that his previous warnings were followed by U.S. military action in June.

He reiterated that the United States is deploying a powerful naval presence to the region. A U.S. naval force led by the aircraft carrier USS Abraham Lincoln arrived in the Middle East, a move U.S. officials say is meant to deter further Iranian escalation.

The deployment follows heightened tensions after Iranian authorities cracked down violently on domestic protests and amid concerns that Tehran could revive its nuclear program.

Iran's mission to the United Nations responded defiantly, accusing the U.S. of past failures in the Middle East and warning that Tehran would defend itself "like never before" if attacked.

Iranian Foreign Minister Abbas Araghchi also denied that Iran is currently seeking talks with Washington, contradicting hopes for a quick diplomatic breakthrough.

The renewed standoff came after Trump withdrew the U.S. from the Obama-era 2015 nuclear deal during his first term, arguing that it failed to stop Iran's path toward nuclear weapons and empowered the regime financially.

Conservatives have long warned that Iran uses diplomacy as cover while continuing to threaten U.S. interests and allies, particularly Israel.

Shamkhani's blunt language appears aimed at deterring further U.S. or Israeli strikes by raising the specter of a broader regional war. At the same time, it reinforces concerns that Iran's leadership remains committed to confrontation rather than reform or compromise.

Trump has repeatedly made clear that the U.S. will not tolerate a nuclear-armed Iran.

Reuters contributed to this report.

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