US President Donald Trump’s administration has delayed a decision on whether to scrap the historic 2015 nuclear deal with Iran, acknowledging that the country is complying with its terms.

Officials told Congress on Monday that despite Mr Trump’s order for sanctions relief to be reviewed in April, interagency findings show that Tehran is following the agreed curbs to its nuclear programme.

The president’s campaign trail proposal to scrap the nuclear deal altogether - which lifted the international sanctions which have crippled Iran’s economy - was widely criticised for endangering an agreement which former Secretary of State John Kerry said “made the world a safer place.”

What happened when US officials were asked why they criticised Iran but not Saudi Arabia

The certification of Iran's compliance, which must be sent to Congress every 90 days, is now the second issued by the Trump administration.

However, Mr Trump, Secretary of State Rex Tillerson and “the entire administration judge that Iran is unquestionably in default of the spirit” of the agreement, one official said, hinting that the US may seek to ratchet up the pressure on Tehran in other ways.

Washington will work with international allies to address flaws in the existing deal such as expiration dates on nuclear restrictions, and consider fresh sanctions over non-nuclear activity, such as the testing earlier this year of ballistic missiles, officials said.

Iran's 'Trumpism' contest Show all 10 1 /10 Iran's 'Trumpism' contest Iran's 'Trumpism' contest A picture taken on July 3, 2017 shows a cartoon of US President Donald J. Trump and First Lady Melania Trump on display at an exhibition of the Islamic Republic's 2017 International Trumpism cartoon and caricature contest, in the capital Tehran. / AFP PHOTO / ATTA KENARE (Photo credit should read ATTA KENARE/AFP/Getty Images) AFP/Getty Images Iran's 'Trumpism' contest An Iranian woman looks at cartoons of US President Donald J. Trump at an exhibition of the Islamic Republic's 2017 International Trumpism cartoon and caricature contest, in the capital Tehran on July 3, 2017. / AFP PHOTO / ATTA KENARE (Photo credit should read ATTA KENARE/AFP/Getty Images) AFP/Getty Images Iran's 'Trumpism' contest An Iranian woman looks at cartoons of US President Donald J. Trump at an exhibition of the Islamic Republic's 2017 International Trumpism cartoon and caricature contest, in the capital Tehran on July 3, 2017. / AFP PHOTO / ATTA KENARE (Photo credit should read ATTA KENARE/AFP/Getty Images) AFP/Getty Images Iran's 'Trumpism' contest Iranian cartoonist Hadi Asadi poses for a picture with a trophy and an award next to cartoons of US President Donald J. Trump, at an exhibition of the Islamic Republic's 2017 International Trumpism cartoon and caricature contest, in the capital Tehran on July 3, 2017. / AFP PHOTO / ATTA KENARE (Photo credit should read ATTA KENARE/AFP/Getty Images) AFP/Getty Images Iran's 'Trumpism' contest Iranians look at cartoons of US President Donald J. Trump at an exhibition of the Islamic Republic's 2017 International Trumpism cartoon and caricature contest, in the capital Tehran on July 3, 2017. / AFP PHOTO / ATTA KENARE (Photo credit should read ATTA KENARE/AFP/Getty Images) AFP/Getty Images Iran's 'Trumpism' contest An Iranian woman looks at cartoons of US President Donald J. Trump at an exhibition of the Islamic Republic's 2017 International Trumpism cartoon and caricature contest, in the capital Tehran on July 3, 2017. / AFP PHOTO / ATTA KENARE (Photo credit should read ATTA KENARE/AFP/Getty Images) AFP/Getty Images Iran's 'Trumpism' contest Iranian reformist cleric Mahmoud Doaei looks at cartoons of US President Donald J. Trump at an exhibition of the Islamic Republic's 2017 International Trumpism cartoon and caricature contest, in the capital Tehran on July 3, 2017. / AFP PHOTO / ATTA KENARE (Photo credit should read ATTA KENARE/AFP/Getty Images) AFP/Getty Images Iran's 'Trumpism' contest An Iranian man looks at cartoons of US President Donald J. Trump at an exhibition of the Islamic Republic's 2017 International Trumpism cartoon and caricature contest, in the capital Tehran on July 3, 2017. / AFP PHOTO / ATTA KENARE (Photo credit should read ATTA KENARE/AFP/Getty Images) AFP/Getty Images Iran's 'Trumpism' contest An Iranian woman looks at cartoons of US President Donald J. Trump at an exhibition of the Islamic Republic's 2017 International Trumpism cartoon and caricature contest, in the capital Tehran on July 3, 2017. / AFP PHOTO / ATTA KENARE (Photo credit should read ATTA KENARE/AFP/Getty Images) AFP/Getty Images Iran's 'Trumpism' contest Iranian reformist cleric Mahmoud Doaei looks at cartoons of US President Donald J. Trump at an exhibition of the Islamic Republic's 2017 International Trumpism cartoon and caricature contest, in the capital Tehran on July 3, 2017. / AFP PHOTO / ATTA KENARE (Photo credit should read ATTA KENARE/AFP/Getty Images) AFP/Getty Images

The US also maintains a separate sanctions list unrelated to nuclear issues which includes terrorism-related offences, human rights abuses, and penalties for support of Syrian President Bashar al-Assad’s government.

Mr Trump’s administration announced the decision just hours before the midnight Tuesday deadline for notifying Congress.

“We receive contradictory signals,” Iranian Foreign Minister Mohammad Javad Zarif said Monday, before the decision was announced. “So we don't know which one to interpret in what way.”

While Monday’s decision to let the status quo stand was expected, the president has not laid out a broader Iran policy, creating a tri-monthly headache in which the White House must decide whether to either support the UN-brokered agreement or claim Iran is breaching it.

Relations between Tehran and Washington have soured quickly since Donald Trump took office.