The U.S. branch of Dentons will combine with Washington, D.C.-based McKenna Long & Aldridge, the firms announced on Wednesday.

The tie-up is set to take effect later this year, making the largest firm in the world even larger, particularly in the U.S. where Dentons will have more than 1,100 lawyers in 21 locations.

If the deal goes through as planned, the newly merged firm will have offices in more than 50 countries and somewhere in the range of 6,600 lawyers, making it far larger than the next biggest firm, Baker & McKenzie, which has about 4,000 lawyers.

Dentons has been on a frenzied merger pace of late: In January, it united with the roughly 4,000-attorney Dacheng Law Offices of China, in a deal structured as a Swiss verein, which allowed the firms to maintain separate profit pools but also to share certain expenses. That merger created the largest firm in the world, a global behemoth governed by a board of 19 directors and combined reported global revenues of more than $1.6 billion.

“At 5 O’clock today, we pulled the partners together to raise a glass of champagne and toast each other,” said Joe Andrew, Global Chairman of Dentons. “Two partners walked up to me to show me – in one case with a Blackberry and in another case an iPhone – where we’re already working on matters together with McKenna Long & Aldridge.”

The deal shows how the legal industry is consolidating, as law firms market themselves to corporate clients as a one-stop shop with offices around the globe.

Firm leaders did not have key details, such as the exact number of McKenna Long’s 400-plus lawyers that will join Dentons. Instead, they said the partnerships from both firms already had approved the merger, and McKenna Long Chairman Jeff Haidet emphasized he expects the “vast majority” of partners to join Dentons. Firm leaders did not cite a proposed date of completion for the tie-up.

“Like most deals, you’re going to have some folks where it’s not the best fit for them,” said Haidet. “We will have some of that, but to what extent, I can’t tell you. I can’t tell you a distinct percentage. We aren’t there yet.”

In 2013, McKenna had discussed, then ended talks for a merger with Dentons. If this merger takes effect later this year, Dentons would add partners in New York, Atlanta, Los Angeles, San Francisco and Washington, DC. Its combination with McKenna also will also put lawyers on the ground in several new cities including Denver, San Diego, Orange County, CA, and Albany, NY.

McKenna Long’s 2014 revenues were not available but the firm reported $345 million in revenue in 2013. It has 15 offices, six in California alone. It also has a small presence outside the U.S., including an office in Seoul, which Dentons said would advance its footprint in the Asia Pacific market, and an office in Brussels.

In a statement, Dentons promoted the deal as giving it a strong boost to its government contract, real estate, intellectual property, insurance, public policy and regulation, corporate, and litigation capabilities.

According to a press release, the merged firm will be led by Co-Chief Executive Officers Haidet, of McKenna Long, and Peter Wolfson, CEO of Dentons US. Mike McNamara,will stay as managing partner of Dentons in the U.S. The firm’s other leadership positions are unaffected.

McKenna Long was formed in 2002 when Washington, DC-based McKenna & Cuneo merged with Atlanta-based Long Aldridge & Norman. In 2012, California-based Luce Forward, Hamilton & Scripps LLP joined McKenna Long. Now, the firm retires its name and becomes part of Dentons US.

Dentons’ Global Chairman Andrew said: “We are the largest law firm in China, and we want to be the largest law firm in the United States – this is the largest legal market.”

Big Law Business Editorial Director Casey Sullivan contributed to this report.