NEW YORK (Bloomberg) — Bermuda-based Assured Guaranty Ltd., the bond insurer backed by billionaire Wilbur Ross, has seen a "breakthrough" in the past month in its efforts to get lenders to buy bad mortgages out of securities the company backs, chief executive officer Dominic Frederico said.

"Activity there has picked up, and we've started to achieve a result I'm incredibly pleased with," Frederico said on an earnings conference call on Friday. "If it continues at this level, it could have a potentially significant impact" on both the company's already recognised losses and potential ones.

Bond insurers including Assured, MBIA Inc. and Ambac Financial Group Inc., stung by record mortgage losses, have sought to undo claims by invoking contracts saying lenders must repurchase loans failing to meet promises about their quality, in some cases filing lawsuits, including against JPMorgan Chase & Co. and GMAC LLC.

Assured, which posted a narrower quarterly net loss after markets closed on Thursday, fell 11 cents to $4.87 in New York Stock Exchange composite trading. The stock is down almost 80 percent since the announcement of Ross's investment a year ago.

While loans from Countrywide Financial Corp., which was acquired last year by Bank of America Corp., made that lender the "poster boy" for Assured's push for repurchases, the insurer also is making requests to other companies, Frederico said. He didn't name them or detail negotiations.

The company has now received about $16.5 million in payments from lenders, up from about $8 million two months ago and compared with the roughly $50 million reduction to previous reserves reflecting expectations for repurchases, Frederico said. Assured may need to "take a hard look" at the size of the reduction, which is small compared with some competitors, if the pace continues, he said.

On Thursday, Assured reported that its fourth-quarter net loss narrowed to $243.8 million, or $2.68 a share, from $260 million, or $3.77, a year earlier. Excluding adjustments, profit was four cents a share, compared with the average estimate of seven analysts surveyed by Bloomberg for two cents.

Assured, which three months ago Moody's Investors Service made one of the last two top-rated bond insurers to lose Aaa grades, has agreed to buy Financial Security Assurance Inc., the other. The deal, expected to close by June 30, may get needed approval from US regulators in March, Frederico said.