US President Donald Trump is expected to voice fresh criticism of Iran later when he chairs a UN Security Council session on the non-proliferation of weapons of mass destruction.
It is only the third time a US leader will have presided over the body.
On Tuesday Mr Trump accused Iran’s leaders of sowing “chaos, death and destruction” in an address to the UN General Assembly in New York.
Iranian President Hassan Rouhani described the US as a “bully”.
Iran is not a member of the security council but President Rouhani is planning to hold a news conference after the meeting.
The war of words continued when US National Security Adviser John Bolton warned Tehran later on Tuesday there would be “hell to pay” if it harmed the US, its citizens or its allies.
The US recently imposed sanctions after leaving the 2015 nuclear deal. The move has exposed divisions between the US and its European allies.
What is expected at the UN?
Wednesday’s session will not be focused on any one particular country but will allow world leaders present to express their views on ways of countering weapons of mass destruction.