Dec. 18 (Bloomberg) -- The ``SuperSIV'' fund, set up to provide cash to structured investment vehicles hurt by the collapse of the subprime-mortgage market, plans to start buying assets ``within weeks,'' its sponsors said today.

The fund's size, originally envisioned at about $80 billion, will be based on ``SIVs' needs and evolving market circumstances,'' Citigroup Inc., Bank of America Corp., JPMorgan Chase & Co. and BlackRock Inc. said in an e-mailed statement. The banks are raising money for the fund to buy assets from SIVs. BlackRock will be the manager.

The urgency that led to the SuperSIV's creation eased after separate SIV bailouts by banks including Citigroup and London- based HSBC Holdings Plc. New York-based Citigroup said last week it would take over seven SIVs with $58 billion of debt. Banks want to avoid forced assets sales to repay SIV borrowings because that would further roil credit markets and reduce the value of their own debt holdings.

The fund, also known as the Master Liquidity Enhancement Conduit, or M-LEC, can still provide ``an optional source of liquidity for eligible high-quality assets,'' the banks said in the statement.

Officials from the banks and BlackRock declined to comment.

SIVs, which sell short-term debt and invest the proceeds in higher-yielding securities, have cut their holdings by more than 25 percent since August to $298 billion, according to Moody's Investors Service in New York. That's when investors started shunning SIV commercial paper and medium-term notes amid increasing losses on subprime mortgages.

Bank of America, based in Charlotte, North Carolina, and New York-based JPMorgan both run money-market funds that own short-term debt issued by SIVs.

Bank of America fell 20 cents to $41.50 at 4:01 p.m. in New York Stock Exchange composite trading, while Citigroup dropped 39 cents to $30.38. JPMorgan declined fell 63 cents to $43.90 and BlackRock rose $1.86 to $205.10.

To contact the reporter on this story: Sree Vidya Bhaktavatsalam in Boston at sbhaktavatsa@bloomberg.net;

Last Updated: December 18, 2007 18:06 EST