By Ransdell Pierson and Ilaina Jonas

NEW YORK, April 10 (Reuters) - Standard & Poor's on Friday cut certain debt ratings of General Motors Corp GM.N and Chrysler Holding LLC [CCMLPD.UL], citing lower likelihood of recovery by their debtors in the event either carmaker defaults on the loans or files for bankruptcy.

The rating downgrades put extra pressure on the two iconic U.S. carmakers, whose already declining fortunes have worsened during the ongoing global economic downturn.

GM, unlike Chrysler, likely would survive in the event of bankruptcy, Standard & Poor's recovery analyst Greg Maddock said in an interview.

"If Chrysler goes into bankruptcy, I would expect it to go into liquidation -- that its assets would be sold in whole or in part," Maddock said. "Instead of being reorganized, there would be no carmaker after bankruptcy."

Maddock cut S&P's rating on General Motors' $4.5 billion senior secured revolving credit facility deeper into junk, due to a shrinking pool of assets available to repay lenders and weak demand for its light vehicles.

"Basically GM is shrinking in terms of the assets they secure," Maddock said. "The debt stays the same."

GM and Chrysler are operating under emergency U.S. government loans. GM has been told by the Obama administration's task force overseeing its bailout that it must cut costs and reduce its debts in order to continue to receive aid.

Chrysler, which has been operating under $4 billion of loans from the task force, has been offered up to $6 billion more if it completes an alliance with Italy's Fiat SpA (FIA.MI: Quote, Profile, Research).