Worldwide losses tied to rotten loans and securitized assets may reach $4.1 trillion by the end of 2010 as the recession and credit crisis exact a higher toll on financial institutions, the International Monetary Fund said.

Banks will shoulder about 61 percent of the writedowns, with insurers, pension funds and other nonbanks assuming the rest, the Washington-based lender said in a report released today on the state of the global financial system. The fund projected losses of $2.7 trillion at U.S. financial institutions, an increase from its estimates of $2.2 trillion in January and $1.4 trillion in October.

Without fiscal stimulus and other government action, banks will probably curtail lending in coming months, worsening the most severe global slump in six decades, the IMF said. Even with forceful state policies, "the deleveraging process will be slow and painful", the fund said.