ANNAPOLIS -- Maryland has maintained its coveted AAA bond rating from all three credit ratings agencies, state Treasurer Nancy Kopp announced.

The ratings agencies weighed in on the state's credit in advance of an upcoming March 6 bond sale.

Maryland is one of nine states to be awarded the highest-possible AAA rating, which keeps interest rates low.

However, Moody's qualified its rating with a negative credit outlook for the state, as it did in July.

Moody's pointed to Maryland's "above average debt burden and large unfunded pension liabilities relative to the size of its economy" to explain the negative outlook.

Maryland doesn't have the cash on hand to pay for $21 billion of its pension obligations.

Moody's also pointed to Maryland's above-average dependence on the federal government.

The other two ratings agencies --Fitch and Standard & Poor's -- gave Maryland bonds a AAA rating with a "stable" outlook.