United States President Donald Trump on Tuesday threatened to attack Iran in retaliation for any attacks by Tehran “on anything American”, after Iran said new US 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.

“In some areas, overwhelming will mean obliteration,” he added.

Fears of war between the United States and Iran have intensified after a US drone was shot down by Iranian forces.

Washington and Tehran disputed the circumstances of the drone shootdown, with Iran saying the unmanned spy plane was downed after it encroached on Iranian airspace, but the US said the aircraft was hit over international territory.

The incident marked the first direct Iranian-claimed attack on US assets and came amid heightened tensions, unleashed by Trump’s decision last year to withdraw from an international accord that curbed Tehran’s nuclear programme.

It was also the latest in an escalating series of incidents in the Gulf since mid-May, including suspected attacks on six tankers, and has prompted international concern alarm that the standoff could escalate into an open confrontation.

•Adapted from an Aljazeera report.