NEW YORK (Reuters) - The U.S. Treasury said on Monday it plans to borrow $617 billion in the fourth quarter, lower than the August estimate, with the decline due to the department’s higher cash balance at the beginning of October. The $617-billion estimate assumes an end-December cash balance of $800 billion, the Treasury said in a statement. The Treasury also said it issued $454 billion in net debt in the third quarter, ending the three-month period with a cash balance of $1.782 trillion. In August 2020, Treasury had estimated privately-held net marketable borrowing of $947 billion and assumed an end-September cash balance of $800 billion. The $493-billion decrease in borrowing was a result primarily of lower-than-assumed expenditures, partially offset by the increase in the cash balance, the Treasury said. For the first quarter of 2021, the Treasury said it plans to issue $1.127 trillion in net marketable debt, assuming an end-March cash balance of $600 billion.