US President Donald Trump predicted on Wednesday that talks with Tehran were imminent, four days after asking Iranian leaders to call him.
"I'm sure that Iran will want to talk soon," Mr Trump tweeted, as he denied reports by The New York Times and The Washington Post about fighting within the administration on Iran's policy and the start of military planning.
“Different opinions are expressed and I make a decisive and final decision. It is a very simple process. All sides, views and policies are covered."
But in Washington, concerns over escalation with Iran and fears – especially among Democrats – of the US being dragged into a military conflict are unsettling Congress.
Politico reported that congressional leaders will hear more information about Iran on Thursday during a confidential briefing with Trump officials.
Senate minority leader Chuck Schumer called on Acting Secretary of Defence Patrick Shanahan and the chairman of the Joint Chiefs of Staff, Gen Joseph Dunford, to testify publicly on Iran.
Republicans appeared to be divided over how to react to the mounting tension.
Senator Marco Rubio defended the administration and called its warnings to Tehran, along with sending two warships and B-52 bombers to the region, defence against the threat of the Iranian Revolutionary Guard Corps.
But other Republicans such as Senator Mitt Romney called it “close to inconceivable” that the administration would consider a war with Iran.
In the region, BBC Arabic reported that Mr Pompeo handed Iraqi Prime Minister Adel Abdul Mahdi a computer memory stick that contained evidence of planned Iranian attacks against US interests through its proxies in Iraq.
The US pulled its non-essential staff from Iraq on Wednesday, and former Iraqi prime minister Ayad Allawi said that Israeli intelligence relayed satellite images of Iranian ballistic missile platforms in Basra city directed towards the Gulf.
But the same BBC Arabic report quoted an Iraqi official as saying Mr Pompeo gave Mr Abdul Mahdi an invitation to be passed on to Iranian officials, asking them "to come to the table".
Mr Adel Abdul Mahdi visited Turkey on Wednesday, while Iraqi Foreign Minister Mohamed Al Hakim this week spoke to the UAE’s Minister for Foreign Affairs and International Co-operation, Sheikh Abdullah bin Zayed.
The UAE’s Minister of State for Foreign Affairs, Dr Anwar Gargash, said on Wednesday that Iran should recognise a need to change its behaviour before full talks could take place.