Trump singled out Iran as a key source of funding and support for militant groups and his words aligned with the views of his Saudi Arabian hosts.
Steve Holland and Jeff Mason
Over the two days, Trump will meet separately with both the Israeli Prime Minister Netanyahu and Palestinian President Abbas and visit holy sites.
Some doubt whether Trump, who has never held elective office before becoming president is ready for a smooth presidential debut abroad.
Trump said he fired Comey over his handling of an election-year email scandal involving then-Democratic presidential nominee Hillary Clinton.
The reversals on Russia and NATO could reassure US allies in Europe who were rattled by Trump’s overtures toward Moscow during the campaign.
In his address to the US Congress, Donald Trump called for national unity, avoiding a repeat of his attacks on Democratic opponents and media organisations.
US President Obama and president-elect Trump met on Thursday for the first time, to discuss the transition to the Republican’s inauguration on January 20.
In a TV show, Trump said that he was surprised that Obama ignored the advice of several experts.