DUBAI/CAIRO — The U.S. and Saudi Arabia launched strikes on Iran-backed groups in Iraq on Wednesday, saying they were responsible for drone attacks on Saudi oil facilities, prompting Iran to warn that blaming it for such attacks was a "major miscalculation." The strikes on targets inside Iraq come as Oman proposed a new regional deal aimed at resolving the conflict over the critical Strait of Hormuz, through which about a fifth of global oil and liquefied natural gas flowed before the war. However, Tehran ruled out Oman's proposal for regional joint management of the strait, saying it had no chance of success, a senior Iranian official told Reuters on Wednesday. The U.S. and Saudi Arabia are trying to pressure Oman to advance their "unrealistic plans" regarding the strategic strait, the official said. Iran's Revolutionary Guards (IRGC) said on Wednesday that its forces struck three oil tankers in the strait and forced them to stop after they ignored warnings for taking an "unsafe and illegal route." The IRGC Navy said in a statement that it continued to maintain full control over the st