CHICAGO, JAN. 18 -- First Chicago Corp. said today it was adding $240 million to its loan loss reserves for the just-ended fourth quarter, and in so doing incurred a loss of $570.7 million for all of 1987.

The additions brought the bank holding company's total reserves for potential losses on foreign loans to $1.32 billion by Dec. 31.

First Chicago said it had a fourth-quarter loss of $96.5 million, compared with earnings of $64.2 million ($1.08 per share) for the same period of 1986.

The full-year loss gave the company its worst annual performance ever, and compared with earnings of $249.2 million ($4.20) for all of 1986.

Many other banks have reported losses or sharply reduced profits for 1987 that were attributed to additions to reserves to cover loans made to such debtor nations as Mexico, Brazil and Venezuela.

First Chicago Chairman Barry F. Sullivan was optimistic that the Latin American debt situation would improve.

"Our decision to increase reserves is based in large part on the increased likelihood that loans to a number of troubled-country debtors will be retired as a result of alternative payment mechanisms," Sullivan said in a statement. "Today's action gives First Chicago greater flexibility to take advantage of such opportunities as they may arise."