"The package of defence equipment and services supports the long-term security of Saudi Arabia and the entire Gulf region," Tillerson told reporters in Riyadh, where President Donald Trump was on his first visit abroad since taking office.

This is "in particular in the face of malign Iranian influence and Iranian-related threats which exist on Saudi Arabia's borders on all sides," Tillerson told reporters in Riyadh.

"Additionally it bolsters the kingdom's ability to provide for its own security and contributing to counter-terrorism operations throughout the region".

Tillerson said the proposed defence packages also cover border security, maritime and air security, air force modernisation, missile defence, cybersecurity and communications upgrades.

The "huge" package will leave Saudi Arabia "more capable of carrying a greater share of the burden of their own security," Tillerson said.