Retired Chief Justice Warren E. Burger says he expects to be released from a Washington hospital within a day, a hospital spokesman said Tuesday. Fern Stone of Sibley Memorial Hospital said Burger told her Tuesday morning that he was suffering from a "mild touch of pneumonia," dehydration and exhaustion and did not expect to stay in the hospital for more than another day. Burger, 81, was admitted Christmas morning. Toni House, Supreme Court spokeswoman, said Monday that Burger told her he was suffering from "a new rare disease: bicentennial exhaustion." Burger, who has chaired the Constitutional Bicentennial Commission since retiring in 1986 as chief justice, was admitted to the hospital briefly last year for back spasms.