Washington (AFP) - The United States approved two large military contracts totalling more than $1.4 billion on Monday after promising Saudi Arabia a huge arms package to counter any threat from Iran.

Last month, on his first foreign trip, US President Donald Trump visited the kingdom and promised its leaders access to $110 billion in weapons and training.

Officials say just under a third of that total was accounted for by contracts approved by the previous administration of Barack Obama, with several more in the pipeline.

Shortly after the deal was signed, the US State Department allowed the Saudi navy to buy a $250 million training package from Kratos Defense and Security Solutions of San Diego.

On Monday, the Saudis got the go-ahead for a $750 million contract to train their air force, working with a variety of US contracted firms.

In addition, the kingdom will spend $662 million on 26 AN/TPQ-53(V) truck-mounted medium-range radar systems, which can pinpoint enemy mortar and missile batteries.

Lockheed Martin will sell the systems and US contractors will provide logistical and training support as the Saudi armed forces deploy them.

During Trump's trip to Riyadh, US Secretary of State Rex Tillerson said the arms deal would help support the long-term security of Washington's partners in the Gulf region.

And he cited in particular "the malign Iranian influence and Iranian-related threats which exist on Saudi Arabia's borders on all sides."

But the unity of the Gulf allies was in question Monday, after a row erupted between Qatar and its neighbors over the gas-rich emirate's alleged support for pro-Iranian groups.

Bahrain, the United Arab Emirates, Yemen and the Maldives joined Saudi Arabia and Egypt in severing relations with Qatar, which hosts the largest US airbase in the region.