US president Donald Trump said he called off talks with Tehran in the latest attempt to pressure the Iranian government beset by nationwide protests.
"I have cancelled all meetings with Iranian Officials until the senseless killing of protesters STOPS," Trump posted on his social media platform on Tuesday, urging the demonstrations to carry on.
Trump said on 11 January that Iran's leaders had reached out to him to negotiate, without providing details. Oman has communicated Iran's openness to talks, according to the White House.
Public demonstrations began in several Iranian cities on 28 December in protest at deteriorating economic conditions, and unrest has escalated in scope and severity, particularly over the past week or so, which has triggered a crackdown by state security forces.
Trump on Monday threatened to impose an extra 25pc tariff on imports from countries engaged in business deals with Iran.
China is Iran's largest trade partner and the primary destination for Iranian crude, which reaches independent refiners through a well-established network of traders and tankers designed to avoid US sanctions.
