NEW YORK (Bloomberg) — Billionaire investor Wilbur Ross said Bermuda-based Assured Guaranty Ltd. doesn't need to raise additional capital and that he plans to talk with Moody's Investors Service about its review of the bond insurer's Aaa rating.

Ross, who committed to invest as much as $1 billion in Assured Guaranty in February and took a seat on its board, said in an interview with Bloomberg Television that he's speaking with investors to allay their concerns. He also expressed support for chief executive officer Dominic Frederico.

"There is no real justification for this review process, let alone for an actual downgrade," said Ross, who lost $91 million on his 13 percent stake in Assured Guaranty as the shares tumbled 40 percent. "I believe the outlook for the company is extraordinarily good."

Assured Guaranty fell $7.43 to $11.32 as of 4:02 p.m. in New York Stock Exchange composite trading, after early dropping as much as 58 percent.

Frederico said in an interview that he learned about Moody's plans just before the ratings company issued its news release.

"You don't take the last two guys who can help municipal issuers and shoot them in the back of the head," Frederico said.