Trump fires his Iran policy architect

US president Donald Trump today fired White House national security adviser John Bolton, a proponent of strong pressure tactic against Iran and Venezuela.

Trump, via his preferred personnel change announcement medium Twitter, said he told Bolton last night that "his services are no longer needed at the White House.

"I disagreed strongly with many of his suggestions, as did others in the Administration, and therefore I asked John for his resignation, which was given to me this morning," Trump said.

The president's decision may have caught his own staff by surprise. The abrupt announcement came less than an hour after the White House announced a special news briefing on sanctions that was supposed to include Bolton, secretary of state Mike Pompeo and treasury secretary Steven Mnuchin.

Bolton, responding via Twitter after Trump's announcement, said he offered to resign last night and "President Trump said, 'Let's talk about it tomorrow.'"

More than any other individual, Bolton had laid out the case for the "maximum pressure" campaign against Iran through sanctions and diplomatic pressure even before becoming Trump's national security adviser in April 2018.

Bolton had argued that the sanctions pressure will either result in the overthrow of the Iranian government or force it to negotiate a new deal on US terms. He suggested that Trump ought to publicly discuss the prospect of talking with Iran after withdrawing the US from the nuclear deal, but only to address his allies' concerns.

But Trump appeared interested in negotiating with Tehran, rather than just going through the motions of a dialogue.

Bolton's policy of maximum pressure has resulted in a near cutoff of Iranian crude exports, but it also has sparked a string of incidents on oil tankers and infrastructure in the Middle East.

The two countries nearly came to a military confrontation in July, but Trump decided not to retaliate after Iran shot down an unmanned US military drone.

Bolton's equally confrontational approach to force out Venezuelan president Nicolas Maduro has not worked out so far.

Trump said he would name a new national security adviser next week and thanked Bolton for his service.