The US will be "relentless" in pressuring Iran over its nuclear programme Mike Pompeo has promised as the Tehran government vowed to ignore "illegal" sanctions reimposed today.
Mr Pompeo called Iran a "destabilising force" in the Middle East and claimed more than 20 countries have cut oil imports from Iran, reducing them by more than one million barrels.
He said the sanctions would accelerate the "rapid decline" of Iran's international economic activity, but he hopes a new deal would be possible.
But Hassan Rouhani, Iran's president, has said his country will "proudly bypass" Donald Trump's "illegal" and "unjust" sanctions by selling oil, and compared the US president to former Iraqi dictator Saddam Hussein.
Mr Rouhani, who also referred to the US as a "bullying power", made the announcement in a meeting with economists that was broadcast on state TV.
He said: "America wanted to cut to zero Iran's oil sales … but we will continue to sell our oil… to break sanctions."
The US measures were imposed on Monday after the Trump administration pulled out of the Iran nuclear deal earlier this year.
Thousands of Iranian students chanted "death to America" in protests that took place on the eve of the sanctions, which target the country's vital oil, shipping and banking sectors.
Oil is a crucial source of hard currency for Iran's struggling economy.
1:05US flags, an effigy of Uncle Sam and pictures of Donald Trump were set on fire in images broadcast on state TV.
The events were timed to coincide with the 39th anniversary of the seizure of the US embassy in Tehran.
Mr Pompeo earlier defended the sanctions and heralded them as the "toughest" ever put in place on the country.
0:37However there are some waivers in place, and Mr Pompeo confirmed he had authorised three for "non proliferation projects", but said they would be "very narrow, very time-limited".
US treasury secretary Steven Mnuchin said he expected European nations to honour the sanctions, but there would be certain humanitarian exemptions.
He said the US is watching Iran with "laser focus".
Iran was hit with its first round of measures in August.
Mr Rouhani said in the meeting on Monday: "I announce that we will proudly bypass your illegal, unjust sanctions because it's against international regulations.
"We are in the war situation.
"We are in a situation of economic war, confronting a bullying power."
Iran's Foreign Minister Mohammad Javad Zarif has said Tehran would consider diplomatic talks with the US if Washington changes its approach to discussing the nuclear deal.
Theresa May was one of a number of world leaders who said they "regret" the US decision to impose sanctions on Iran.
Her spokesman said: "We continue to believe that the Iran nuclear deal makes the world a safer place and our position remains that as long as Iran continues to meet its obligations under the deal by respecting strict limits on its nuclear activity, we will be committed to it too."
The Iran nuclear deal was drawn up by the Obama administration and was agreed to by the UK, Russia, France, China, Germany and the EU.
International financial and economic sanctions were lifted in return for Tehran curbing its disputed nuclear activity under UN surveillance.
Donald Trump posted a Game of Thrones-style image on Twitter on Friday, which showed him striding in front of a moody grey background.
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Mr Trump had the words "Sanctions are coming, November 5" across his chest.
The font was the same as that used in the hit TV drama and the wording is a riff on one of its famous lines "winter is coming".
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