Leading Texas firm Baker & Botts has set up a temporary office in London and is in the process of looking for permanent space.
Jay Kolb, head of the firms Moscow office, has been transferred to London to run the operation.
Kolb is believed to have been a driving force pushing for the office, which is the firms first in western Europe and second outside the US.
Joel Swanson, partner at the firms Houston head office, said: One of our primary strengths is in major international energy projects and many energy projects are now focused on or financed in London.
He added that the firm also wanted to service a client, Azerbaijan International Operating Company, a consortium of oil companies developing oil and gas reserves in Azerbaijan, which is increasingly coordinating pipeline and export contracts in London.
The firm is looking to relocate other lawyers to its new office, although no final decision has been made on the number. It is not looking for UK lawyers.
The firm follows in the footsteps of Akin Gump Strauss Hauer & Feld, another large Texas firm with a strong Russian and energy practice, which set up a London office last year. Other Texas firms that have bases in the capital include Vinson & Elkins and Fulbright & Jaworski.