With home prices likely to slip further in 2012 the risk of jumbo mortgages, yet to refinance out of security pools, will be at a growing risk of strategic default, Moody’s Investors Service said in a forecast Thursday.

Stronger prime jumbo borrowers refinanced last year, leaving weaker ones still in residential mortgage-backed securities. More than 80% of these loans are still current, Moody’s said, but more than half of them are underwater.

The credit ratings agency said it still expects high losses on RMBS in 2012. The performance of these products stabilized in 2011. Delinquency levels remained flat and even dropped. But delays in the foreclosure process and still elevated inventories of repossessed homes will push home prices down again.

Subprime has almost entirely burned out with the worst mortgages already defaulted. Alt-As and option adjustable-rate mortgages show more risk, but no product is more concerning to Moody’s than jumbos.

“The high level of negative equity and limited opportunities to refinance will continue to amplify the rate of strategic default, primarily in prime jumbo pools,” Moody’s said.

New issuance of private-label RMBS is expected to be dry this year as the government-sponsored enterprises continue to dominate and regulatory uncertainty keeps other entrants at bay. Although, Redwood Trust (RWT) is in the process of bringing a $415 million deal to market.

As for the availability of credit in the coming year, Moody’s said it doesn’t expect lending requirements to loosen at least at the largest lenders.

“Bank will continue to originate pristine mortgage loans, although some new players will originate non-prime loans,” Moody’s said.

Write to Jon Prior.

Follow him on Twitter @JonAPrior.