The Boston law firm Nixon Peabody is in merger talks with Blank Rome in Philadelphia, two sources familiar with the talks said on Friday.

The two U.S. law firms have been in discussions for at least two months, according to a third source with direct knowledge of the talks. The merger would create the 33rd-largest U.S. law firm, according to financial figures for the year 2012 reported to the legal trade magazine American Lawyer.

Blank Rome managing partner Alan Hoffman declined to confirm or deny the merger discussions, though he said no merger was imminent.

"I talk to firms all the time," Hoffman said. "I heard one rumour that we're going to merge with Nixon Peabody in January and that's completely false. We are not on the verge of merging with anybody."

Nixon Peabody Chief Executive Andrew Glincher did not immediately respond to requests for comment. A spokeswoman for the firm declined to comment on any merger talks.

Nixon Peabody, with more than 600 lawyers in the United States, Europe and Asia, specializes in advising corporations and financial institutions on regulatory matters, litigation and corporate transactions. In 2013, it represented investment company StoneCastle Financial Corp, media company Gannett Co Inc and drinks company Constellation Brands Inc, according to press statements by the firm.

In December the firm hired Brian Kelly, the former U.S. Attorney who tried gangster James "Whitey" Bulger. Kelly was the latest high-ranking government official to be employed by the firm.

Both Nixon Peabody and Blank Rome have government affairs practices. In March, Nixon Peabody hired Scott Brown, the former U.S. Senator from Massachusetts, in its Boston office.

Blank Rome has nearly 500 lawyers in the United States and Shanghai, and specialises in corporate litigation, labor and employment, government relations, real estate and bankruptcy.

In July, the firm represented data company IHS Inc in a $1.4 billion acquisition of automotive business R.L. Polk & Co.

At least 87 mergers among U.S. law firms have been announced in 2013, a particularly active year, according to legal consultancy Altman Weil.

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