March 13 (Bloomberg) — The credit rating of the University of California, the biggest U.S. system combining education, research and health care, was cut one level by Moody's Investors Service on rising debt and reduced state support.

Moody's lowered its rating to Aa2, third highest, and assigned the same grade to $950 million in revenue bonds scheduled to be sold April 3. The downgrade yesterday affects $18.5 billion in debt for the university system, which operates 10 campuses and five hospitals. The outlook is stable.

The university, which Moody's said had total system revenue of almost $24 billion in fiscal 2013, relies on the state for about 10 percent of its budget. State funding has declined about 25 percent over the past five years when adjusted for inflation, said Dianne Klein, a university spokeswoman.