BOSTON – A Virginia energy company on Friday proposed building a liquefied natural gas terminal on an uninhabited island in Boston Harbor, pitching it as an alternative to bringing tankers near the city or a proposed facility in Fall River that’s met heavy public opposition.

AES Corp. said the site – an unused state park land known as Outer Brewster Island – would have two key benefits: more storage capacity than an existing Distrigas terminal in Everett and farther from residential neighborhoods than the Fall River proposal.

“The region needs an LNG facility; it doesn’t need two or three,” said Aaron Samson, managing director of AES’s liquefied natural gas projects division. “It gives us the public safety protection of an offshore facility while giving us the reliability of a land-based facility.”

Currently, tankers traverse the busy harbor under armed guard out of concern they could be attacked by terrorists and explode. The biggest tankers cannot fit under the Tobin Bridge, which spans a portion of the inner harbor.

James W. Hunt, the chief of energy and the environment for the city of Boston, said: “From what we’ve seen conceptually, we think it’s a proposal at least worth considering, especially given our concern about ships traveling into Boston’s inner harbor. This is a proposal worth considering from a homeland security and energy security standpoint.”

Gov. Mitt Romney called the plan “very interesting and very valid.”

He contrasted it with the Fall River proposal, which he said “I don’t like,” adding: “I far prefer the idea of LNG storage facilities and ports offshore, away from populated areas.”

Under the plan, tankers would stay out of Boston Harbor while offloading liquefied natural gas. The gas would be stored in two tanks built into granite quarries, before being vaporized and sent into an existing undersea pipeline 1.2 miles away.

The site is out of the path of normal harbor traffic, as well as the flight paths for Logan International Airport. It also would not have the warm-water discharge of LNG terminals suggested for buoys off Gloucester, about 35 miles north of Boston, a concern of the region’s fishermen and lobstermen.

It also would be more remote than the existing facility in Everett, just outside of Boston, as well as the proposed facility in Fall River. The nearest residents are 2 miles away in Hull, and downtown Boston is 10 miles away.

The proposal would require approval of two-thirds of the Legislature because the island is currently under the control of the state Department of Conservation and Recreation. The island is the second-outermost among the string of islands in the Boston Harbor Island park system.