WASHINGTON, Sept. 18 (AP)  The Senate unanimously approved legislation on Tuesday night that would require equal health insurance coverage for mental and physical illnesses when policies cover both.

The bill builds on 1996 legislation that lifted major restrictions on mental health coverage by adding provisions on co-payments, deductibles and length of treatment. The House is considering a similar bill that has 270 co-sponsors, more than half the House membership.

The bill, passed by unanimous consent, moves advocates one step closer in their quest for mental health parity.

“The passage tonight of the Mental Health Parity bill underscores our commitment to treat all patients facing all diseases with the dignity and respect they deserve,” said Senator Edward M. Kennedy, a Massachusetts Democrat and a co-sponsor. “This new legislation will bring dramatic new help to millions of Americans who today are denied needed mental health care.”