Qatar has signed a $12bn deal to buy F-15 fighters jets from the US.
The sale was finalised at a meeting in Washington between US defence chief Jim Mattis and his Qatari counterpart.
It comes days after US President Donald Trump accused Qatar – a major US ally – of funding terrorism “at a very high level” – a charge Qatar denies.
Other Gulf countries recently cut ties with Doha, accusing it of destabilising the region through its alleged support of extremist groups and links to Iran.
Qatar is home to the biggest US air base in the Middle East, Al-Udeid. It houses around 10,000 troops and plays a key role in the US-led operations against the so-called Islamic State (IS) group in Syria and Iraq.