The Post said officials became aware of the UAE's role in the hack after newly analyzed information gathered by members of the USA intelligence community revealed senior members of UAE's government discussed the plans and how to implement the attack.
The US sources alleged UAE officials had discussed the planned hacks on May 23, just days before they occurred, but added that it remained unclear whether the UAE carried out the hack itself or paid another entity to do so.
United States spies now believe those comments to have been concocted and planted on Qatari government websites. Funding, supporting, and enabling extremists from the Taliban to Hamas and Gaddafi.More news: England batsmen versus SA bowlers key contest in World Cup semi
Qatar had repeatedly said that the website of the Qatar News Agency's was hacked but failed to provide the results of its own investigation so far.
The crisis has raised concern of economic consequences as well as growing instability in the region, home to some of the world's largest energy exporters and key Western allies which host USA military bases.
The small but fabulously wealthy gulf kingdom is also regarded as too close to Iran, by its neighbours.
Initially the United States seemed to have taken sides with them against Qatar in the dispute, President Trump accusing the Qataris of funding terrorism "at the highest level".
Several bankers, including two at Qatari institutions involved in the proposed deal, told Reuters that the refinancing had been indefinitely postponed as the crisis had deterred Gulf banks from doing new business with Qatar and tightened liquidity in the domestic Qatari money market.
But the Trump administration has sought a more even-handed approach since.
"We've sent a message to Qatar".