FARGO (AP) - North Dakota State University's debt has more than doubled in the past five years, but officials say its bond rating and ability to pay off debt remain strong.

Financial figures show NDSU has $117.8 million in debt, compared with $51.4 million in 2003.

John Adams, NDSU's vice president for finance and administration, said a growing enrollment means more revenue and the ability to absorb more debt.

"As your financial picture expands, then your capacity to handle more debt expands as well," Adams said.

NDSU has had a major bonding project each year since 2004 for residence halls, its Memorial Union expansion or a fitness center addition. The projects were financed with 30-year revenue bonds, which are paid back using student fees and other revenue generated by the buildings.

NDSU will ask the Legislature this spring for permission to borrow another $20 million to build campus apartments to ease a housing shortage. A consultant's report says a $14 million parking ramp also is being discussed.

If the Legislature approves, state Board of Higher Education members will review the request more closely to look at bonding limitations, said Laura Glatt, the state university system's vice chancellor for administrative affairs.

"Obviously, NDSU is in a pretty good financial situation with growing enrollment, and they obviously have to solve their housing problem," Glatt said.

Adams said NDSU officials work closely with their financial adviser and Moody's Investor Services to determine how much borrowing is appropriate. The key factor is the university's ability to handle the debt, he said.

NDSU spent 2.3 percent of its operating budget on interest payments in fiscal year 2007, and the school seeks to keep that ratio under 5 percent, he said.

"The ratio has come down a little bit over the years as we've added debt, but it's still within tolerable limits," Adams said.

Moody's has assigned an A1 bond rating to NDSU, meaning upper-medium grade.

The most recent report from Moody's says NDSU's financial strengths are its enrollment growth, expected growth in state funding and an increase of resources during the past decade. The report says NDSU's growing debt as is financial challenge.

Other challenges are endowment assets that remain modest relative to the university's ambitions and a projected 23 percent decline in high school graduates through 2017.

The most recent financial review by the North Dakota University System said NDSU should carefully evaluate the impact of additional debt.

Similar advice was given to the University of North Dakota, which had $105 million of debt as of June 30. UND spent nearly 2.5 percent of its operating budget on interest payments in fiscal year 2007.

Valley City State University and Mayville State University spent slightly more of their operating budgets on debt that year, the financial reports said.