President Donald Trump has banned foreign nationals from studying at Harvard University in the latest escalation on his clash with the Ivy League institution.

The president issued an executive order Wednesday entitled Enhancing National Security by Addressing Risks at Harvard University, which suspends the Ivy League's student visa program - declaring that is a 'privilege granted by our government, not a guarantee.'

He also doubled down on his claims that the school violated federal law, and argued it is important to limit international students for national security as he also restricted travel from a dozen countries.

'The Federal Bureau of Investigation has long warned that foreign adversaries and competitors take advantage of easy access to American higher education to, among other things, steal technical information and products, exploit expensive research and development to advance their own ambitions and spread false information for political or other reasons,' the executive order states.

'Our adversaries, including the People's Republic of China try to take advantage of American higher education by exploiting the student visa program for improper purposes and by using visiting students to collect information at elite universities in the United States.'