The deal was completed despite the Gulf country being criticized recently by U.S. President Donald Trump for supporting terrorism.
Qatar News Agency (QNA) reported the arrival of the vessels on Wednesday, the same day that Qatar signed an agreement for the purchase of F-15 fighter jets from the USA with an initial cost of $12bn.
While Trump appeared to back Saudi Arabia and Tillerson took a more neutral tone, the Defense Department underscored its relations with Qatar, saying the U.S. was grateful to the country for its support of the United States presence there.
Attiyah said the agreement would boost Qatar's defences and create 60,000 jobs in the United States.
The Qatari defense ministry issued a statement Wednesday celebrating the F-15 deal.
As the rift between Qatar and the Saudi-led bloc enters its second week, Mevlut Cavusoglu, Turkey's foreign minister, has said that Qatari authorities does not want the diplomatic crisis to continue. "We believe that this agreement will propel Qatar's ability to provide for its own security while also reducing the burden placed upon the United States military in conducting operations against violent extremism". Al Udeid Air Base is home to more than 11,000 US and coalition troops.
Qatar on Thursday said that preparations for the 2022 World Cup were unhindered, having secured alternative supplies of construction materials to those that had been coming by land from Saudi Arabia.
A member of the Saudi delegation, led by the country's transport minister, said they would not be meeting directly with the Qatar representatives. More than 100 aircraft operate from there.
Kuwait's Emir Sheikh Sabah Al Ahmad Al Sabah has launched a mediation effort after Saudi Arabia, the United Arab Emirates, Bahrain and Egypt severed ties with Qatar, accusing it of sponsoring terrorism.
Erdogan said he had never witnessed Doha supporting terrorism, adding Turkey "will continue to give all kinds of support to Qatar". He's also due to travel to Saudi Arabia.
Mattis and Secretary of State Rex Tillerson have urged a conciliatory approach to the Gulf standoff, but Trump's comments last week broke with this tone.