Iranian President Hassan Rouhani has lambasted the Trump administration, saying the White House is "afflicted by mental retardation", The Independent has reported.
His words come after Trump imposed sanctions on the country's supreme leader, Ayatollah Ali Khamenei, and other senior figures, following Iran's shooting down of a US drone.
Speaking in a live address on Tuesday, according to a translation by Sky, Rouhani said: "How can a person lose their mind so badly and do something so outrageous and idiotic by sanctioning the leader of a country? They are suffering from mental disability. The White House is afflicted by mental retardation and does not know what to do."
He added: "The White House actions mean it is mentally retarded. Tehran's strategic patience does not mean we have fear."
In addition, he claimed the sanctions would lead to the "certain failure" of US policy and added that they showed Washington is "lying" about their offer to negotiate.
In the meeting with ministers, broadcast live on TV, he said: "At the same time as you call for negotiations you seek to sanction the foreign minister? It’s obvious that you’re lying."
His comment that the White House is "mentally retarded" is a remark that Iranian officials have made in the past about Trump, but is the first time Rouhani's own comparatively measured tone has changed.
Trump imposed sanctions after Iranian forces shot down a US surveillance drone that they alleged had violated Iranian airspace over the Strait of Hormuz.
The US insisted the drone was flying over international waters, and Trump was minutes away from a retaliatory air strike when he decided at the last moment that too many people would die if it went ahead.
The American president has stated that he is responding to recent "aggressive behaviour" and "increasingly provocative actions" by Iran with the sanctions.
The US has also accused Iran of being behind two sets of explosions that have damaged six oil tankers in the region, with Iran firmly rejecting the allegations.
The dispute follows a pattern of heated tensions between the two countries, escalating back in May 2018 when Trump withdrew from a 2015 multilateral pact with Iran in which the Western Asia country agreed to limit its nuclear programme in return for the lifting of crippling economic sanctions.