Australian Foreign Affairs Minister Julie Bishop and US Secretary of State Mike Pompeo have opened the Australia-US Ministerial meetings in California amid a diplomatic storm between the US and Iran.

The annual AUSMIN talks, also attended by Australian Defence Minister Marise Payne and US Defense Secretary James Mattis, began as US President Donald Trump heightened world tensions with an angry, all capitalised tweet threatening Tehran.

The AUSMIN talks are expected to also broach sensitive topics including China’s territorial aggression in the Indo-Pacific, the ongoing North Korea nuclear talks, trade and infrastructure.

Ms Bishop and Mr Pompeo did not answer reporters’ questions when they met on Monday to shake hands before cameras at Stanford University’s Hoover Institution, where the two day meeting is being held.

A small group of protesters yelling anti-Trump chants gathered outside the building under the watch of security personnel.

Mr Trump, after his recent controversial trip to Europe and talks with Russian President Vladimir Putin, unleashed an angry mostly capitalised tweet to Iran’s leader Hassan Rouhani on Sunday.

Iran’s Foriegn Minister responded Tuesday morning (AEST), saying Tehran was unimpressed with his latest missive, and advising the US President to “BE CAUTIOUS”.

COLOR US UNIMPRESSED: The world heard even harsher bluster a few months ago. And Iranians have heard them —albeit more civilized ones—for 40 yrs. We’ve been around for millennia & seen fall of empires, incl our own, which lasted more than the life of some countries. BE CAUTIOUS!

— Javad Zarif (@JZarif) July 23, 2018

The tweets have the potential overshadow AUSMIN by taking the attention of Mr Pompeo and Mr Mattis.

Mr Trump earlier warned Mr Rouhani to “NEVER, EVER THREATEN THE UNITED STATES” saying Iran would “SUFFER CONSEQUENCES THE LIKES OF WHICH FEW THROUGHOUT HISTORY HAVE EVER SUFFERED BEFORE”.

To Iranian President Rouhani: NEVER, EVER THREATEN THE UNITED STATES AGAIN OR YOU WILL SUFFER CONSEQUENCES THE LIKES OF WHICH FEW THROUGHOUT HISTORY HAVE EVER SUFFERED BEFORE. WE ARE NO LONGER A COUNTRY THAT WILL STAND FOR YOUR DEMENTED WORDS OF VIOLENCE & DEATH. BE CAUTIOUS!

— Donald J. Trump (@realDonaldTrump) July 23, 2018

Trump’s tweet came after Rouhani warned the Trump administration was playing “with the lion’s tail”.

Pompeo, in a speech on the weekend, angered Iran when he said the US supports Iranian protesters who took to the streets to oppose corruption and call for expanded rights.

“America should know that peace with Iran is the mother of all peace, and war with Iran is the mother of all wars,” Rouhani said.

-AAP