General Dan Caine, chairman of the US Joint Chiefs of Staff, has privately cautioned President Donald Trump and top aides that a military strike on Iran carries serious risks, including a prolonged conflict, substantial casualties, and depleted munitions, according to US officials familiar with the discussions.

Caine, who has been outlining a spectrum of military options from limited strikes to wider operations aimed at regime change, has taken a measured approach in his assessments amid an unprecedented US military buildup in the Middle East.

His private advice contrasts with Trump’s public statements, in which the president has repeatedly claimed that any conflict would be “easily won.”

This week, Trump denied media reports suggesting that Caine had counselled against military action, asserting the accounts were inaccurate and reaffirming his confidence in the general’s leadership.

The developments come as the United States and Iran prepare for another round of nuclear talks in Geneva.

Trump has set deadlines for Tehran to accept stricter terms or face unspecified consequences, while Iran maintains it seeks a diplomatic resolution.