One of the lenders in a huge downtown Dallas development project is moving to force a sale of the property.

GCP Income Opportunities I LLC says that in April it loaned $55 million toward the redevelopment of the 52-story former First National Bank tower in downtown. The Elm Street high-rise is being converted into a mixed-use project valued at more than $350 million.

The Texas lender, which provided debt for the deal, had declared the project in default and is seeking a sale to repay the loan, according to filings with Dallas County. A trustee has been appointed to "sell the property to satisfy a portion or all of the indebtedness."

California-based Drever Capital Management has been working for two years to convert the vacant skyscraper at 1401 Elm St. into a combination of apartments, retail, office space and hotel rooms.

Drever Capital Management acquired the landmark Dallas building out of bankruptcy and restarted construction after the previous owners ran out of cash. The developer said that the project is moving ahead, and new financing is in the works.

"We remain in ongoing discussions with the lender," a Drever spokesman said in an email. "While we are on track in closing new financing, construction continues and we are looking forward to completing construction on schedule in 2019."

The legal filings give the lender the ability to purse a forced sale but does not necessarily mean a foreclosure would take place.

Trustee appointments for sales can be used as a bargaining tool between lenders and borrowers. Often the disputed debt is paid off or refinanced. The borrower can also seek court protection to halt a foreclosure.

The skyscraper project — called The Drever — is the largest-ever redevelopment in Dallas.

The more than 1-million-square-foot building dates to 1965 and has been vacant almost a decade.

The city of Dallas has agreed to provide $50 million in financial incentives to give the old skyscraper a new life. Drever has so far been financing the project with a combination of debt, private investment dollars and personal equity contributions.

The tower is the last major downtown Dallas building awaiting a redo.

The project is even larger than the just-completed Statler Hotel renovation, which cost more than $250 million.