Just two days after taking the job of chief executive, Vikram Pandit has moved swiftly to tackle the problems at Citigroup, deciding to shift $49 billion of assets from investment affiliates known as structured investment vehicles, or S.I.V.'s, onto its balance sheet early next year.

The move seems certain to derail an effort, led by Citigroup, Bank of America, and J.P. Morgan Chase and orchestrated by the Treasury Department, to create a superfund that would buy assets from banks' S.I.V.'s

Citigroup said that its action is independent of the group effort and that it still supports a superfund, or a "Master Liquidity Enhancement Conduit."

But Citigroup is the biggest player in S.I.V.'s, with an estimated quarter of the market, and its bailout appears to make the creation of a superfund no longer as critical for the market's liquidity as it once seemed.

The "super S.I.V.," as the Financial Times' Alphaville blog notes, "looks increasingly an anachronism. The concept has been overtaken by events."

Citigroup said the decision was in response to a warning by the credit-ratings agency Moody's Investors Service on November 30 that it might lower the ratings on $65 billion of assets in Citigroup's seven S.I.V.'s. (Citigroup has been steadily unloading its S.I.V. assets, from $87 billion in August to $49 billion today.)

"Our team has made great progress managing the S.I.V.'s in a very difficult environment," Pandit said in a statement. "After considering a full range of funding options, this commitment is the best outcome for Citi and the S.I.V.'s."

After the Citigroup announcement, Moody's lowered Citigroup's credit rating to Aa3 from Aa2, citing the prospect that the bank would take additional write-downs.

The decision on the S.I.V.'s came after Citigroup said that Robert Druskin, its chief operating officer, would leave, another sign that Pandit intends to reshape the bank's management and strategy.

Citigroup's bailout follows similar measures by HSBC of Britain and Société Générale of France.

Although Citigroup said it still intends to make its capital targets next year, the decision to take in the S.I.V.'s will eat into its capital base, putting pressure on the bank to cut or eliminate its dividend.

"If they don't sell enough other assets to make room for this stuff, they are going to have issues," Christopher Whalen, the managing director at Institutional Risk Analytics, told the New York Times. "The $7.5 billion from Abu Dhabi was great, but they are going to have to raise more capital in 2008, perhaps as much as three times that amount.