Mashantucket Pequot Gaming Enterprises President Michael Speller leaves after 18 months on the job

The head of Foxwoods Resort Casino has quit his job, creating further uncertainty around the largest casino in the United States as it negotiates with lenders to restructure debt.

Michael Speller, president of the Mashantucket Pequot Gaming Enterprises, resigned "effective immediately," the Mashantucket Pequot Tribal Council disclosed Monday, just 18 months into the job. The tribe owns the giant casino, which is located on federally designated reservation land in southeastern Connecticut.

Speller took the top job at Foxwoods in December 2008, just after a major expansion that added a new casino, the MGM Grand at Foxwoods, and significantly enlarged the tribe’s $2 billion-plus debt load.

But as revenues declined amid the recession, Speller and the Pequots were forced to confront restructuring the debt amassed over the years to fund the 6.7 million-square-foot resort. The tribe has been negotiating with banks and bondholders for months ahead of a repayment deadline in July, according to sources cited The Wall Street Journal.

The circumstances surrounding Speller's departure were unclear, the Journal reported. A spokeswoman for the casino wouldn’t say. Speller couldn't be reached for comment, the newspaper said.

The tribe said casino veteran William Sherlock, who once served as president and chief executive of Foxwoods, would take over as interim president while a replacement for Speller is sought.

The debt controversy also has played out at the highest levels of the Pequots’ government. Chairman Michael Thomas was forced out in January after promising tribal members they would retain the generous per capita payments they receive from the casino, an assurance that alarmed major creditors such as Bank of America and Wells Fargo.

Banks and bondholders haven’t much leverage, however. The tribe, as a federally designated sovereign nation, cannot be forced to reorganize under federal bankruptcy laws. Neither can creditors foreclose on tribal assets, including Foxwoods, which can only be owned and operated by the Pequots.

Thomas was replaced by Rodney Butler.