The NFL has dropped its plan to challenge approved dementia diagnoses in a landmark concussion case as players' lawyers accuse the league of trying to delay payments and rewrite the $US1 billion ($A1.4 billion) settlement.
A federal court hearing set for Thursday on the NFL's appeal was cancelled on Wednesday following the move with US District Judge Anita Brody issuing an order requiring doctors to explain their findings in certain cases.
The NFL had asked to challenge some diagnoses made by settlement-approved doctors and upheld by a court-appointed administrator whose decisions are supposed to be final.
The league nonetheless filed an appeal on the grounds that the standards used to diagnose the ex-players with dementia were not being applied consistently.
The NFL argued that it had agreed to remove a $US765 million ($A1.1 billion) cap on payouts only in exchange for "a clear demarcation of the boundary between compensable and non-compensable levels of impairment."
Some players' lawyers said the NFL is having buyer's remorse as the early payouts surge past early projections in the 65-year settlement.
Plan administrators have approved more than $US600 million ($A837 million) in claims, and paid out $US425 million ($A593 million), in the first two years alone.
In contrast, the NFL had thought it would take a decade to pay out the first $US400 million ($A558 million), according to a lead players lawyer who called the league's appeal "meritless."
"Our advocacy on behalf of former players will continue to ensure they receive every benefit under this agreement, and that the NFL pays every dollar for which they are obligated," the lawyer, Christopher Seeger, said in a statement Wednesday.
Messages seeking comment were left with an NFL spokesman.
Retired players can seek awards of as much as $US3 million ($A4.2 million) for moderate dementia and $US1.5 million ($A2.1 million) for mild dementia, although most men would get far less. The settlement resolves thousands of lawsuits that alleged the NFL hid what it knew about the risk of concussions in order to return players to the field.
The settlement offers retired players baseline testing and compensation for four types of illnesses - Alzheimer's disease; Parkinson's disease; multiple sclerosis; and dementia.
