By "accrued leave time," we assume you mean accrued paid time off or PTO (e.g. vacation time). If so, while you can request leave without pay, the employer is not required to grant it; the employer only must give you the specific or actual benefit you have, which would be a certain amount of earned paid leave. They do not need to let you miss work without pay. The employer could voluntarily choose to give you leave without pay if the employer chose.