LONDON — Israel’s fledgling natural gas industry was rattled Tuesday over a threat by the country’s antitrust regulator to break an American-Israeli group’s hold on the country’s gas resources.

Israeli officials and the antitrust regulator have said that they are concerned that Noble Energy, a Houston-based oil company, and its partners, Delek Drilling and Avner Oil Exploration, had a lock on Israeli gas production.

Noble and its partners produce nearly all of Israel’s gas from an offshore field called Tamar, and that gas is used to generate about half of the country’s electric power. They are developing a larger field, Leviathan.

Together, the Leviathan and Tamar fields hold an estimated 800 billion cubic meters of gas, enough to meet current Israeli demand for about a century. With such a wealth of gas, the companies and the government are backing plans to also export gas to Israel’s neighbors.

Given significant reliance on the gas in Israel, the regulator is objecting to the group’s dominant position over the two fields. One worry is that Noble and its partners could overcharge for the gas, hurting consumers.

Israel’s antitrust commissioner, David Gilo, said he would hold a hearing for the companies before making a decision.