WASHINGTON (Reuters) - President Donald Trump on Tuesday threatened to attack Iran in retaliation for any strikes by Tehran "on anything American," after Iran said new U.S. sanctions precluded any diplomacy and called the White House actions "mentally retarded."

"Iran's very ignorant and insulting statement, put out today, only shows that they do not understand reality. Any attack by Iran on anything American will be met with great and overwhelming force. In some areas, overwhelming will mean obliteration," Trump said in a Twitter post.

The United States imposed sanctions on senior Iranian officials, including Supreme Leader Ayatollah Ali Khamenei, on Monday. U.S. sanctions on Foreign Minister Mohammad Javad Zarif are expected later this week.

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Tensions between the two long-time foes have escalated over the last month, when Washington blamed Tehran for attacks on two oil tankers and Iran downed a U.S. surveillance drone. Tehran has denied responsibility for the tanker attacks and has said the U.S. drone was flying in Iranian airspace.

Trump said he called off a strike on Iran last week in retaliation for the drone incident, after he decided at the last minute it would kill too many people.