A rare public dispute over oil policy in Saudi Arabia emerged Tuesday as billionaire Prince al-Waleed bin Talal disagreed with the kingdom’s energy minister over the potential impact of falling oil prices on the Arab state’s economy. In an open letter to the kingdom’s oil minister, Ali al-Naimi, and the cabinet dated Oct. 13, the influential Saudi prince expressed his astonishment at how Mr. Naimi has played down the impact of the recent fall in oil prices. “As we have repeatedly warned in the past…our country faces the danger of continuing to depend almost entirely on oil,” Prince al-Waleed said in the letter. “The kingdom’s 2014 budget is 90% dependent on oil revenues, so belittling [the impact of falling oil prices] is a catastrophe that cannot go unmentioned,” he said. The Saudi prince, a nephew of Saudi King Abdullah, is a major international investor with stakes in Apple Inc., Citigroup Inc., Time Warner Inc., Twitter and News Corp, which owns Dow Jones & Co., publisher of The Wall Street Journal. He warned last year that the kingdom’s petroleum-dependent economy is increasingly vulnerable as rising production of U.S. shale oil and gas reduces global demand for crude from members of the Organization of the Petroleum Exporting Countries.