The deal would create a firm of some 4,000 lawyers in offices in 32 countries.
As part of the move Chadbourne & Parke will disappear with the new firm opertaing under the Norton Rose Fulbright title.
London-based Norton Rose Fulbright is already a heavyweight in the global legal marketplace with some 3,700 lawyers.
Chadbourne is best-known for advising banks on project finance deals around the world but it also garnered attention when the firm’s litigation department represented Democratic members of Congress during President Bill Clinton's 1999 impeachment hearings.
Daryl Lansdale, Norton Rose’s managing partner for the Americas said both firms had complementary practices.
Both firms represent energy companies and advise on deals in Latin America.
Some of the clients both firms currently represent are Deutsche Bank AG , Banco Santander SA and French energy company Engie SA.
Norton Rose Fulbright saw a 3 per cent dip in global revenue in its last financial report down to $1.732 billion in global revenue, which it blamed on volatile exchange rates during the fiscal year.