NEW YORK, March 11 (Reuters) - Moody's Investors Service said on Tuesday it is reviewing the Alt-A segment of the residential mortgage-backed securities market amid ongoing deterioration in the U.S. housing market.

The review will focus on many of the Alt-A loan pools that were originated during late 2005 and 2007 and are exhibiting higher-than-expected rates of delinquency and foreclosure and repossessions by banks.

"The actions are part of a wider review of all RMBS transactions, in light of the deteriorating housing market and rising delinquencies and foreclosures," said Amy Tobey, vice president of Moody's RMBS Surveillance Group.

The Alt-A segment spans a spectrum of credit quality and performance, ranging from near-prime to near-subprime.

Over the last week, bid lists containing Alt-A and prime mortgage bonds have emerged in the secondary market, joining the fray of subprime mortgage securities up for sale. Recent margin calls were the drivers behind the SALES OF in the "AAA" prime and Alt-A space, according to traders and investors.

Moody's said it will continue to announce results of the review on an ongoing basis over the coming two to three months.

Because the Alt-A sector exhibits significant variation in performance, Moody's said, rating adjustments will vary based on current ratings, level of credit enhancement, deal-specific performance, quarter of origination and collateral characteristics, as well as other qualitative factors.

Last week, Fitch launched its own review on $160 billion of Alt-A mortgage transactions due to rapid deterioration in the housing market over recent months. The review also affects loans made between 2005 and 2007.

Fitch said it will first focus on the $10 billion of subordinate Alt-A RMBS, which face more substantial pressure from rising mortgage defaults. (Editing by Dan Grebler)