President Donald Trump on Tuesday threatened to attack Iran in retaliation for any strikes 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.

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

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 US surveillance drone. Tehran has denied responsibility for the tanker attacks and has said the US 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.

Earlier, US National Security Adviser John Bolton said Washington was still willing to talk to Iran.

“The president has held the door open to real negotiations to completely and verifiably eliminate Iran’s nuclear weapons program, its ballistic missile delivery systems, its support for international terrorism and other malign behavior worldwide,” Bolton said in Jerusalem. “All that Iran needs to do is to walk through that open door.”

The US backed out of the 2015 international agreement curbing Iran’s nuclear program in May last year and has ramped up sanctions against the country.

The US will look for ways to impose even more sanctions in the future unless Tehran changes its behavior, according to US disarmament ambassador Robert Wood.

“We will look to see what more we can do on sanctions,” Wood said Tuesday as he left the Conference on Disarmament in Geneva, the world's main nuclear negotiating forum, where he had traded sharp accusations with an Iranian diplomat.

Iran’s ambassador to the United Nations, Majid Takht Ravanchi, told reporters on Monday that Iran would not agree to talks with the US while it is under the threat of sanctions.

Iran’s Foreign Minister Mohammad Javad Zarif, responding to the sanctions said hawkish politicians close to Trump “despise diplomacy, and thirst for war.”

Bolton was speaking at the start of a meeting with his Israeli and Russian counterparts that was expected to focus on Iran and Syria.

-Reuters