Financial Corp. of America, the nation's largest savings and loan association, said yesterday it expects 1984 losses between $500 million and $700 million.

The losses, greater than expected, were caused by increases in the company's provisions for possible losses on loans and real estate investments, said William J. Popejoy, FCA's chairman and chief executive.

Popejoy said he made the announcement today in response to recent speculation that the company's 1984 losses are going to be greater than expected when results are officially released.

The troubled California thrift lost about $7 billion in deposits last year after the Securities and Exchange Commission forced it to restate its second-quarter earnings. One analyst said yesterday he is concerned that unanticipated losses may be even higher than those announced by the company.

Thomas D. Klingenstein, an analyst with Wertheim & Co., said the key issue is whether FCA, which is under the close supervison of the Federal Home Loan Bank Board, will be able to maintain depositor confidence. The company's stock, which closed yesterday at 6 1/2, up 1/2, on 2.77 million shares, has fallen from a recent high of about $11 a share, Klingenstein said.