Congress has indicated it plans to ensure the US complies with the Iran nuclear deal despite President Donald Trump lambasting the agreement, the European Union's top diplomat said.

In wide-ranging comments in Washington Federica Mogherini also called mounting tension between Saudi Arabia and Iran "extremely dangerous," saying the world "seems to go completely crazy," and implicitly criticised the US on human rights.

Last month Mr Trump decertified the 2015 Iran deal which curbed the country's nuclear programme in exchange for relief from international economic sanctions.

Mr Trump said he believed Iran was breaching the spirit of the agreement but did not urge scrapping it entirely as he did during his election campaign.

Instead, he urged Congress to spend 60 days establishing "very firm trigger points" that would lead to sanctions being automatically reimposed.

Ms Mogherini said she got "clear indications" from members of Congress that the US would remain "compliant" with the agreement.

Speaking after talks with US politicians, she said: "I got clear indications that the intention is to keep the United States compliant with the agreement."