NEW YORK (Reuters) - Assured Guaranty Ltd (>> Assured Guaranty Ltd.) can move forward with part of a lawsuit accusing UBS AG (>> UBS AG) of falsely representing the quality of the loans underlying $1.49 billion of mortgage-backed securities it insured, a federal judge has ruled.

The lawsuit is one of several filed since the financial crisis hit monoline insurers over losses they sustained insuring mortgage-backed securities when the housing market tumbled. Other monolines with similar lawsuits against banks include MBIA Inc (>> MBIA Inc.) and Ambac Financial Group Inc.

U.S. District Court Judge Harold Baer, in Manhattan, on Wednesday kept Assured's claims alive, though he dismissed a portion of the case.

Baer allowed Assured to press ahead with claims that UBS breached contracts underlying the securities by misleading the insurer about the quality of the mortgages.

He dismissed a claim that accused UBS of breaching obligations to repurchase defective mortgage loans. Baer said only the trustee for the trusts underlying the mortgage-backed securities could make such a demand.

Assured Guaranty has demanded UBS buy back $1.6 billion in loans, the bank said in an April court filing. In its complaint, Assured said it had by the end of January paid out $308.2 million in claims related to the securities.

Ashweeta Durani, a spokeswoman for Assured Guaranty, said the company was in the process of reviewing the decision.

UBS declined to comment through a spokesman.

Assured has similar lawsuits pending against units of JPMorgan Chase & Co (>> JPMorgan Chase & Co.), Credit Suisse (>> Credit Suisse Group AG) and Flagstar Bancorp Inc (>> Flagstar Bancorp, Inc.). It reached settlements with Bank of America (>> Bank of America Corp) for $1.1 billion and Deutsche Bank (>> Deutsche Bank AG) for $165.6 million, without filing lawsuits against them.

Assured sued UBS in February after the bank declined to repurchase hundreds of millions of dollars worth of mortgages. The lawsuit, which claimed breach of contract, focused on financial guaranty insurance Assured provided in 2006 and 2007 to three mortgage-backed securities transactions.

The policies, as was common at the time, provided that Assured would cover losses if cash flows from the mortgages were not enough to pay investors what they were owed.

In his ruling, Baer also said Assured could sue UBS for allegedly breaching another set of agreements by providing "false and misleading data" to Standard & Poor's and Moody's in an effort to procure inflated credit ratings for the securities. Assured had made any insurance conditional on the securities being rated AAA or slightly below.

Assured's stock rose 5.6 percent to $14.16 in late day trading on the New York Stock Exchange.

The case is Assured Guaranty Municipal Corp. V. UBS Real Estate Securities, Inc., U.S. District Court for the Southern District of New York, 12-cv-01579

(Reporting by Nate Raymond; Editing by Leslie Adler, Bernard Orr)

By Nate Raymond