Taking the unusual step for a Saudi businessman to go public with his concerns, Alwaleed published a letter online during the weekend that warned the country's finance minister, Ali al-Naimi, that demand for oil from the Organization of Petroleum Export Countries cartel was "in continuous decline."
The prince said the use of the fracking process to extract gas and oil in other countries, including the United States, threatens oil-rich Saudi Arabia.
Naimi said in May that rising U.S. shale oil supplies would not be a problem for oil exporters.
Sky News reported Monday that Alwaleed's letter was dated May 13, 2013.
The letter says that the country should take "swift measures" to diversify its economy.
About 92 percent of the Saudi Arabian government's budget for 2013 is made up of oil money, Sky News said.
"It is necessary to diversify sources of revenue, establish a clear vision for that and start implementing it immediately," Alwaleed's letter said.
Alwaleed also recommended the country cut its own oil consumption and develop plans for nuclear energy and solar power projects.