The new chairman of Citicorp said today that the world's largest bank company will add a "number" of its loans to Argentina to its problem list Wednesday because their interest payments become 90 days overdue.

John Reed, in his first press conference since becoming Citicorp chairman Sept. 1, said that Argentina must come to terms with its internal economic problems -- escalating inflation, a large budget deficit and an overvalued peso -- before major banks can renegotiate the terms of the country's roughly $25 billion in foreign bank debt.

In a statement after Reed's breakfast meeting with reporters, a bank spokesman said that Citicorp expects its Argentine problem loans will grow by $50 million to $75 million before the end of the year. At the end of September about $500 million of Citicorp's $1.2 billion in loans to Argentina were past due.

Banking sources said that other major banks probably will see an increase in their problem loans to Argentina during the final three months of the year, but whether the increases will be smaller or larger than those expected at Citicorp depends on a number of factors, including when payments were due and whether the loans are to the government, private industry or to Argentine banks.

All told, U.S. banks have loaned about $8.5 billion to Argentina, and a large number of those loans already are on problem lists. Argentina's total foreign debt -- including money owed non-U.S banks, other countries and multinational organizations -- is about $45 billion.

Argentina has paid interest on official loans through April 24. Government loans with interest payments due on July 24 become three months overdue Wednesday. Other loans will be added to the list in coming weeks.

Loans to Argentine banks, including the central bank, are fully current, sources said, and lenders do not face the prospect of adding them to their problem lists.

Loans put on problem lists are a drag on earnings. On a performing loan, banks count the interest as if it were paid every day, even though the actual payment is scheduled to be made only every three or six months. When a loan goes on the problem list, the interest that had been accrued must also be removed from bank earnings.

Banking sources said that the increase in Argentine problem loans will not be as great in the final three months of the year as in the second and third quarters because most of the loans that are in arrears already are listed as problem -- or more technically, nonperforming -- loans.

Argentina last week asked its 320 bank lenders to renegotiate the terms on about $20 billion in loans that have come due or will by the end of the year, and also asked them to lend it another $5.45 billion between now and the end of 1985.

Reed said that Argentina's economic agreement with the International Monetary Fund last month is designed to deal with the internal economic problems. If Argentina follows the terms of that agreement, then it will be possible to restructure Argentina's repayment.