BOSTON — The Wampanoag tribe on Martha’s Vineyard says a U.S. agency cleared the way for a casino-style gambling hall on the Massachusetts island favored by U.S. presidents for summer vacations.

“We are announcing that we will probably be the first gaming site” in the state, Cheryl Andrews-Maltais, the chairwoman of the Wampanoag Tribe of Gay Head, said Tuesday in a conference call with reporters. “We’ve been able to secure our federal approvals.”

The announcement elicited shock in the State House, where legislative leaders have fought plans to bring gambling to the Vineyard, as it’s known, for decades. The gaming hall would be in Aquinnah, near the Gay Head bluffs, one of the most exclusive areas in one of the wealthiest enclaves in the state.

The American Indian tribe received a legal opinion from Eric Shepard, the acting general counsel of the National Indian Gaming Commission, last month. Shepard said the Wampanoags are eligible to build a class 2 casino, which can include slot machines and card games such as poker, according to a letter the tribe provided. The tribe owns 485 acres in the town of Aquinnah, which is the Wampanoag term for Gay Head.

The tribe will open a temporary slot parlor at a community center within months with “hundreds, not thousands,” of the gaming machines, Andrews-Maltais said. The tribe also plans to build a permanent facility on the island, she said.

“We want to be sure we are consistent with the modesty we think should be there,” Andrews-Maltais said. “We want to be sure we don’t overbuild.”

Andrews-Maltais said she doesn’t need any additional local or state approval to move forward with the plans. The Wampanoags of Gay Head make up one of five Wampanoag branches in Massachusetts, including the Mashpee tribe on nearby Cape Cod.

Heather Johnson, a spokeswoman for Gov. Deval Patrick, declined to comment Tuesday, saying the governor’s office hadn’t received formal notice of the plan. Martha’s Vineyard can only be reached by air or boat, and the state operates a ferry service connecting residents and vacationers to Cape Cod.

Aquinnah Selectman Spencer Booker, who is a Wampanoag, said the tribe would need the town’s permission to move forward with the project, citing municipal lawyers. Booker said the town would challenge the tribe in court if it went ahead with its plans without seeking local input.

“Our town lawyers have said unequivocally that the tribe would need permission from the town,” he said by telephone.

Massachusetts lawmakers are currently in the midst of enacting a new gambling law intended to bring three casinos and one slot parlor to other parts of the state.