The online auction for Little Gull Island has been extended at least until Friday, after a bid of $280,000 was placed with the General Services Administration shortly after noon on Thursday.

The New London Maritime Society, which has been raising money to purchase the island, appealed to the GSA in an email Thursday to allow it to buy the island even though it is not the high bidder, Susan Tamulevich, director of the society, said.

“We have not given up,” she said. “We’re only more vehement that we want to preserve this historic property and the ecological setting.”

Tamulevich said that in its message to the GSA, the society said it can pay $150,000 for the island, and that its track record with other historic structures and partnerships with conservation groups should be a deciding factor. The island, located in eastern Long Island Sound, is home to a 143-year-old granite lighthouse. It is also considered an important area for shorebirds.

“We can be the perfect steward for this property,” she said.

The society has raised funds with the help of Save the Sound and also set up an online fundraising site at http://en.indiegogo.com/Save-Little-Gull-Island.