Trump staff restricted access to president's 'suspicious' calls with Saudi crown prince

White House staff attempted to restrict access to US President Trump's phone calls with controversial Saudi Crown Prince Mohammed bin Salman, sources told CNN Friday.

Trump aides would take extraordinary steps to ensure that information from the president's calls with the Saudi crown prince were not made public.

The aides said that additional security checks were put in place to restrict access to transcripts of telephone exchanges between Trump and Prince Mohammed.

They described steps taken, such as transferring the transcript into a code word computer system, as unusual given the nature of the calls with big implications.

"In my experience you would never move a transcript to the code word system if it does not have any code word terms. If the president is classifying and declassifying stuff he doesn't want to get out, that is an abuse of power and abuse of the system," said Sam Vinograd, a CNN national security analyst who worked with two presidents.

The sources said the calls did not include highly senstive national security information prompting suspicions about the steps taken by aides to guard the transcripts.

Officials would usually been given a rough of transcripts of the president’s calls with world leaders but were not provided one after Trump's conversation with the Saudi crown prince.

Mohammed bin Salman has come under fire for being linked to the murder of journalist Jamal Khashoggi, while Trump is considered close to the crown prince.

He refused to distance himself from the de-facto Saudi ruler following the allegations linking him to the murder, nor condemn him for his absymal human rights record which included a crackdown on pro-democracy campaigners and women's rights' activists.

The same was true of conversation calls with Russian President Vladimir Putin, who has been accused of helping to get Trump elected over Hillary Clinton during presidential elections.

The security system used to protect the transcripts is the same one that held Trump's conversation with the Ukraine president, sparking a whistle-blower to reveal information of the calls.

Trump faces a possible impeachment case over the call.