The lawyer told Reuters that Patton Boggs's managing partner, Edward Newberry, sent a memo to partners, saying the firm is getting "independent advice" from legal consultancy Zeughauser Group, as well as Wells Fargo, and Deloitte and PricewaterhouseCoopers on the proposed merger.

The lawyer spoke on the condition of anonymity because he was not authorized to speak publicly.

Newberry did not immediately respond to a request for comment.

The memo, according to the lawyer, said that Patton Boggs had not yet committed to a merger with Locke Lord, but that the firm was undergoing a "due diligence" process in which it will examine pension and benefits, client conflicts and risk and liability.

Representatives from Patton Boggs and Locke Lord did not immediately respond to requests for comment. Neither did representatives from Zeughauser Group, Wells Fargo, Deloitte or PricewaterhouseCoopers.

Reuters was first to report, on October 27, that Patton Boggs, which has nearly 500 lawyers and public policy advisers, was in talks to merge with a larger U.S. law firm. Two former Patton Boggs partners told Reuters that the potential suitor was Locke Lord, which has more than 650 lawyers and consultants.

The 51-year-old Patton Boggs is known for its influence on Capitol Hill and has represented a number of large companies and institutions this year including AT&T , Goldman Sachs and Amazon.com Inc (>> Amazon.com, Inc.) in their lobbying efforts, according to OpenSecrets.org, which publishes information on lobbying.

Locke Lord, which is known for its energy, litigation and insurance practices, has recently represented companies such as Natural Gas Partners, Argent Energy and White Deer Energy, in acquisitions and financing arrangements, according to its website.

Both firms have represented parties in litigation arising from the September 11 attacks on the United States.

Patton Boggs ranked No. 95 out of U.S. law firms for revenue in 2012 at $317.5 million and No. 91 in profits per partner at $735,000, according to figures published in the American Lawyer, a legal trade publication. Locke Lord ranked No. 69 for revenue in 2012 at $428.5 million and No. 65 in profits per partner at $1.07 million, according to the magazine.

(The story was refiled to clarify in second paragraph to show Patton Boggs is receiving "independent advice" from legal consultancy Zeughauser Group)

(Reporting By Casey Sullivan; Editing by Noeleen Walder and Ken Wills)

By Casey Sullivan

Stocks treated in this article : Wells Fargo & Co, Argent Energy Trust, Amazon.com, Inc.