US Secretary of State Marco Rubio defended joint US-Israeli strikes on Iran, saying “the world will be safer”.
Oman had been mediating talks between Iran and the US before Washington attacked Tehran.
Iran is launching attacks across the Gulf region after the US-Israel operation against the country.
Trump appeared to dismiss Reza Pahlavi as an option and sketched a vision of Iran's government similar to Venezuela's.
US President Donald Trump said Iranian dissident Reza Pahlavi could be a possible successor to Ayatollah Ali Khamenei.
Primaries will determine party candidates in November race to control Congress, give early window into voter sentiment.
US Navy 'will begin escorting' oil tankers through the Strait of Hormuz, a strategic waterway, if necessary, Trump says.
The development comes after an Iranian-made drone crashed into the UK's military base in Cyprus.
Flames and black smoke were seen rising from the US Consulate in Dubai after a suspected attack.
Thousands gathered in Minab, Iran, for a mass funeral of 165 schoolgirls and staff killed in a US-Israeli airstrike.