U.S. banks and government officials face mounting pressure to address concern that firms mishandled mortgage and foreclosure documents. Shares of Bank of America Corp. and Wells Fargo & Co. yesterday fell the most in more than two months amid uncertainty about defective mortgages. Paul Miller, an analyst at FBR Capital Markets in Arlington, Virginia, raised his estimate for the cost of litigation and delays to banks to $10 billion yesterday from $6 billion. An investigation by attorneys general in all 50 states into banks’ foreclosure practices fueled speculation about even greater losses if mortgage-bond investors successfully challenge the underlying loans and force lenders to buy them back. Industry experts also said faulty foreclosures may lead banks to agree to principal writedowns. “The nation has been in denial about the scope of the problem, and it’s now just being revealed,” said Janet Tavakoli, founder of Chicago-based Tavakoli Structured Finance Inc., a financial consulting firm, in a phone interview. “This is a huge crisis for our country.”