"Secretary of Defence Jim Mattis met on 14 June (Wednesday) with Qatari Minister of State for Defence Affairs Khalid al-Attiyah to discuss concluding steps in finalising the Foreign Military Sales purchase of US-manufactured F-15 fighter aircraft by the State of Qatar", said Pentagon spokesman Lt.Col. Roger Cabiness.
Qatar and the USA finalized Wednesday a $12 billion military deal for procurement of F-15 fighters by Qatar amid the Gulf Crisis opposing the tiny Arab state to its regional neighbors led by Saudi Arabia.
U.S. agrees with KSA/UAE that Qatar is a "state-sponsor of terrorism", and then sells Qatar $12 billion in arms.
According to Bloomberg News, Qatar bought 36 warplanes produced by McDonnell Douglas, a subsidiary of Boeing.
A statement to CNN from the Pentagon says the agreement will "increase security cooperation and interoperability between the United States and Qatar".
Hours later, at a press briefing, Trump said "The nation of Qatar, unfortunately has historically been a funder of terrorism at a very high level" and recalled his attendance at the Arab-Islamic American Summit in May as an inciting incident for the blockade.
USA officials stressed neutrality towards the conflict at the time, highlighting the thousands of US troop based out of Qatar and its close relationship with Saudi Arabia.
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All of this comes just a day after the Ambassador from the United Arab Emirates suggested the U.S. should move their base out of Qatar to "pressure" them.
Qatar is an important base for the U.S. military carrying out operations against Islamic State militants and other groups in Iraq, Syria, Afghanistan and beyond.
The crisis has put Turkey in a delicate position as Ankara regards Qatar as its chief ally in the Gulf but is also keen to maintain its improving relations with the key regional power Saudi Arabia.
The US vessels - the USS Chinook and the US coastguard cutter Baranof - docked in Hamad Port, south of Doha, according to the US 5th Fleet based in neighboring Bahrain - one of the countries to have frozen ties with Qatar.
He will travel to Saudi Arabia for more talks on Friday.
Bahrain and the UAE have also banned expressions of sympathy for Qatar.
"For now, we are working to bring these states together towards a solution which satisfies both their current regional concerns and the global needs and expectations of passengers and shippers", the statement said.
However, it remains unclear how the organization that doesn't issue binding rules could force the Arab nations to reopen their airspace to Qatar.