TACLOBAN, the Philippines — Typhoon gridlock threatened rescue operations in the most devastated part of the Philippines on Wednesday, with aid piling up but few ways to distribute it, plentiful gasoline but no merchants willing to sell it, and an influx of emergency volunteers but no place to house them.

The intensifying frustrations of delivering aid after Typhoon Haiyan struck last week elicited a plea from the top United Nations relief official to the mayor of Tacloban, imploring him to persuade gas station owners to open so relief convoys could begin a large-scale expansion into the flattened port city of 220,000 and interior regions of Leyte Province. The gas stations have fuel in their tanks, but the owners fear theft and violence if they reopen.

“We have to have fuel, so we have to have some kind of refueling center,” Valerie Amos, the United Nations official, told the mayor, Alfred S. Romualdez, at a public meeting after she flew here for an assessment.

Mr. Romualdez told Ms. Amos that the city could not easily cope with the influx of aid workers, as practically no vehicles were available to bring them in from the airport, while food and drinking water were running out. “I’m asking those who come here, ‘Please be self-sufficient, because there’s nothing,’ ” he said.