HOUSTON — The operator of the largest petroleum pipeline between Texas and New York, which was shut down after a ransomware attack, declined on Sunday to say when it would reopen, raising concerns about a critical piece of infrastructure that carries nearly half of the East Coast’s fuel supplies.

While the shutdown has so far had little impact on supplies of gasoline, diesel or jet fuel, some energy analysts warned that a prolonged suspension could raise prices at the pump along the East Coast and leave some smaller airports scrambling for jet fuel.