NEW YORK (Reuters) - U.S. ratings agency Standard & Poor's on Tuesday cut the credit rating of billionaire investor Carl Icahn's Icahn Enterprises (>> Icahn Enterprises LP) to junk status after the portfolio absorbed declining investment values and higher leverage in the last few months.

S&P dropped the long-term issuer credit rating and senior unsecured debt rating of Icahn Enterprises to double-B-plus from triple-B-minus, the agency said in a statement.

Additionally, S&P said it removed all of Icahn Enterprises' ratings from "CreditWatch" with the outlook at "Stable."

There was no immediate response to an email to Icahn's office seeking comment.

Shares in Icahn Enterprises closed down 0.42 percent at $52.53.

The downgrade reflects Icahn Enterprises' elevated loan-to-value ratio, which S&P now expects to remain between 45 percent and 60 percent over the next 12 months, said S&P Global Ratings credit analyst Clayton Montgomery.

"While part of this increase in leverage has come as the portfolio (most notably CVR Energy, Federal Mogul, and the investment segment) has deteriorated in value over the past year, it has also resulted from a substantial decrease in the amount of cash at IEP, which we net against debt in our LTV calculation," Montgomery said.

As of March 31, Icahn Enterprises's LTV ratio was approximately 50 percent, S&P noted. "However, we estimate that after quarter-end through May 13, 2016, IEP's large publicly traded positions declined by approximately $600 million, which would result in an LTV ratio of about 53 percent, holding all else equal."

S&P said the investment segment of Icahn Enterprises declined again in the first quarter, losing 12.8 percent of its value, after having negative returns in both 2015 and 2014.

"We would view further losses in this segment negatively, not only because it would have a leveraging effect on IEP's LTV ratio, but also because it would further pressure IEP's liquidity profile," S&P said.

As of March 31, Icahn Enterprises's investment in the investment segment and cash covered debt by 37 percent, down from 65 percent as of Dec. 31, and 96 percent as of March 31, 2015.

It was revealed Monday that Icahn exited some of his big holdings during the first quarter. Icahn sold out of positions in Gannett Co Inc (>> Gannett Co Inc), Tegna Inc (>> Tegna Inc) and Mentor Graphics Corp (>> Mentor Graphics Corp).

Among his earlier moves that had previously been disclosed, Icahn sold his stake in Apple in the quarter, a $4.8 billion position that had been his largest outside holding at the year-end.

(Reporting By Jennifer Ablan; Editing by Tom Brown and Alan Crosby)