An employee previously awarded impairment benefits by OWCP may file a claim for additional impairment benefits. Such claim must be based on an increase in the employee's impairment rating attributable to the covered illness or illnesses from the impairment rating that formed the basis for the last award of such benefits by OWCP. OWCP will only adjudicate claims for such an increased rating that are filed at least two years from the date of the last award of impairment benefits. However, OWCP will not wait two years before it will adjudicate a claim for additional impairment that is based on an allegation that the employee sustained a new covered illness.