Iran too 'great' to be intimidated: Rouhani

Iran's President Hassan Rouhani has pledged the Islamic republic is "too great to be intimidated by anyone" in a late night meeting with clerics.

"God willing we will pass this difficult period with glory and our heads held high, and defeat the enemy," Rouhani said late Monday as he met Sunni clerics to mark the holy Muslim month of Ramadan, the official government website dolat.ir said.

He was speaking after four ships, including two Saudi oil tankers, were reportedly attacked off the UAE coast on Sunday, in a sign of mounting regional tensions.

Iran has called for an investigation into what it called an "alarming" incident.

Iran and the United States have engaged in a war of words in recent weeks since Tehran began to roll back commitments set out in a landmark 2015 nuclear deal with world powers.

US President Donald Trump withdraw the United States from the deal last year and has unilaterally reimposed stringent sanctions on Iran.

Last month, Washington designated Iran's revolutionary guards as a "foreign terrorist organisation", the first time that part of a foreign government has been branded as such.

The dispatch of the USS Abraham Lincoln carrier group plus an amphibious assault ship, a Patriot missile battery and B-52 bombers by the US to the region has triggered fears of possible military clashes.