LONDON — The British and Gibraltar authorities will soon release an Iranian oil tanker that has been held for more than a month, an Iranian official said on Tuesday, signaling a possible step toward de-escalating tensions between Tehran and the West that threaten world energy supplies.

Officials in Gibraltar and London would not confirm or deny the Iranian claim about the impending release of the tanker, the Grace 1, which was seized on July 4 off the coast of Gibraltar.

Jalil Eslami, the deputy head of Iran’s maritime agency, predicted the release at a news conference, and his remarks were reported by several Iranian news organizations with ties to the government.

“We believe that Grace 1 oil tanker will resume operation under Iranian flag in international waters in the very near future,” Mr. Eslami said, according to the Fars news agency. PressTV quoted him as saying, “Certain documents have been exchanged, which would help settle the issue.”