PORTLAND, Me.  As community mental health systems fray under the strain of state budget cuts and a weak economy, law enforcement officers across the nation are increasingly having to step in to provide the emergency services that clinics have typically offered the mentally ill.

Police and sheriff’s departments that are already grappling with budget and manpower cuts say the situation is further straining their resources and forcing them to divert officers from their regular duties. It has also stoked fears among law enforcement officers of dangerous encounters between the police and people with severe mental illness.

“I worry that there’s going to be a tragedy,” said James Craig, chief of the Police Department here, where calls involving the mentally ill increased to 1,645 in 2009 from 1,424 in 2007. “I’m worried that an officer might lose his life dealing with a dangerous person, a person who really needs treatment.”

Improving the department’s handling of the mentally ill became one of Chief Craig’s biggest priorities last year after an officer was forced to dangle off the Casco Bay Bridge as he pulled a woman to safety during a suicide attempt. She was released from a hospital hours later and tried to jump off the bridge again.