WASHINGTON—Hit by a cyberattack, the operator of a major U.S. fuel pipeline said it hopes to have services mostly restored by the end of the week as the FBI and administration officials identified the culprits as a gang of criminal hackers. U.S. officials sought to soothe concerns about price spikes or damage to the economy by stressing that the fuel supply had so far not experienced widespread disruptions, and the company said Monday that it was working toward “substantially restoring operational service” by the weekend. The White House said in a statement late Monday that it was monitoring supply shortages in parts of the Southeast and that President Joe Biden had directed federal agencies to bring their resources to bear. Colonial Pipeline, which delivers about 45 percent of the fuel consumed on the East Coast, halted operations last week after revealing a ransomware attack that it said had affected some …