The Fed is taking another step to help the markets.

This morning, the central bank announced further measures to address the liquidity problems facing financial institutions caught up in the mortgage mess. The Fed said it will lend up to $200 billion to securities dealers for periods as long as four weeks, rather than overnight, which is the current policy.

Stocks rallied on the Fed move. At 11:30 a.m. ET, the Dow Jones Industrial Average was up 216 points to 11,956 after losing 153 points on Monday. As of Monday’s close, the Dow had lost 546 points, or 4.3%, this month and had shed 11.5% for the year.

This morning, the Nasdaq Composite Index had gained 44 points to 2,214, and the Standard & Poor’s 500 Index had added 22 points to 1,296.