BTR Realty Inc. said yesterday that it has leased a full floor of the five-story Gateway International II office complex at Baltimore-Washington International Airport to the American Telephone & Telegraph Co., pushing occupancy at the struggling building to about 60 percent.

"It's not a see-through building anymore," said Carolyn Brown, a spokeswoman for a public relations firm retained by the Linthicum developer.

The 125,000-square-foot building is 15 months old, and its high vacancy rate has been a problem for BTR, a publicly traded company whose stock has fallen sharply since the real estate recession began. The company's stock closed unchanged yesterday at $2.

"Interest rates are down," BTR president F. Patrick Hughes said. "For the degree of leasing we have, the degree of debt we have, we have enough in there to say 'Yeah, we're there.'" Mr. Hughes said the project has variable-rate financing, so BTR's debt costs have fallen in recent months.

Mr. Hughes said the AT&T; divisions involved, which he declined to name, are now at 400 E. Pratt Street in Baltimore.

He said Gateway II "could be 80 percent leased" by the end of the year.