Lamont is calling for Connecticut’s two federally recognized Indian tribes to drop longstanding plans for an East Windsor casino in exchange for sports betting and other enticements, officials said. A source close to the negotiations said the state has discussed selling the troubled XL Center in downtown Hartford to the tribes, who would renovate and add gambling and other amenities to the arena. The “global solution” that Lamont is pushing has been rejected so far by the Mashantucket Pequot and Mohegan tribes, who have spent nearly $20 million in planning, design and demolition costs in fighting for years to build the $300 million East Windsor casino. The XL Center is operated by the Capital Region Development Authority. The authority has failed in efforts to sell the arena and more recently has discussed asking the state for $100 million in improvements.