Carleton M. Stewart, the former chairman of the American Security Bank, yesterday disclosed that he is taking over the chief executive job of the International Resources and Finance Bank in London.

Stewart, 59 -- who spent about 20 years abroad, including a stint with Citicorp in London, before joining American Security in 1976 -- left the area's second-largest bank in March after policy disagreements with the bank's board.

The International Resources and Finance Bank is a three-year-old, $250 million operation in London that is largely controlled by Middle East interests. The chairman of the bank is Hani Emam, of Saudi Arabia. The bank specializes in Middle Eastern projects but offers full commercial banking.

During Stewart's tenure at American Security, the bank expanded the scope of its operations, raising the bank's assets to $2.4 million. Even though the bank built up its international divisions, and in 1978 passed arch-rival Riggs National Bank in profits, differences in management style and emphasis ultimately led to Stewart's departur from the bank.

Stewart, in a statement, said that "directing the affairs of American Security was most interesting and rewarding. My wife and I have spent many years in the international world, and we now look forward to re-establishing our home in London."