WASHINGTON, March 11 (Reuters) - The Financial Accounting Standards Board has promised to issue new mark-to-market accounting guidance for banks struggling to price assets in an illiquid market, the head of the U.S. Securities and Exchange Commission said Wednesday. "FASB has committed to us that the guidance will be out in the second quarter ... We are continuing to push them," SEC Chairman Mary Schapiro said at a hearing by a House Appropriations subcommittee on the agency's annual budget needs. The mark-to-market accounting rule is defended by investor advocates and some lawmakers as a way to give investors a clear picture of what assets are held on banks' books. But the banking industry, which has been forced to write down billions of dollars' worth of hard-to-value assets in the illiquid markets, has pleaded for a suspension or modification of the rule. On Tuesday, Federal Reserve Chairman Ben Bernanke said he favored "some improvements" to address what he described as the "weak points" of mark-to-market accounting. A separate House panel has scheduled a Thursday hearing to examine what kinds of incremental fixes to the rule might be possible. Schapiro also said she hoped the SEC would issue a proposal in April aimed at restoring the so-called "uptick rule" that restricts short-sellers. The uptick rule, adopted after the 1929 stock market crash, allowed short sales only when the last sale price was higher than the previous price, but was abolished by the agency in 2007.