"The Gulf countries are not a stable, unified bloc, but rather a group of uneasy neighbors with a history of intrigue and machinations against each other," the report said.
According to published reports, the Trump administration plans to float the idea of a Middle East Strategic Alliance (MESA) of six Gulf nations, plus Egypt and Jordan, to counter Iranian influence in the region.
However, Saudi Arabia and the United Arab Emirates (UAE) have continued a "pointless and counterproductive" campaign to isolate fellow Gulf Cooperation Council member Qatar, the report noted.
In addition, the Saudi and UAE armed forces still require US support to operate effectively, despite dramatically upgraded military capabilities, according to the report.
The Saudi-led air campaign in Yemen illustrates Saudi and UAE military weakness, with little more than a humanitarian disaster to show for their three-year effort to dislodge rebels that control the capital, Sanaa, and much of Western Yemen, the report pointed out.