Amor Group, which provides IT systems for the energy, public service and transport sectors, retains Grayling for corporate work while Lockheed retains Hill+Knowlton Strategies.
However, the review has been prompted by the need to have a single agency overseeing the account.
The rethink comes amid a wider strategic repositioning for Lockheed Martin UK aimed at developing new commercial partners.
The company's EMEA head of comms John Nielson explained that diversifying was part of wider growth in the UK which he claimed had seen the number of staff employed rise from 2,000 to more than 3,000 in the last year.
Highlighting the recent win of a contract to manage the Ministry of Justice's IT systems as an example, he said: "We are continuing to grow at a dramatic rate, with a lot of business not in the traditional defence sector.
"A key part of the focus of the brief will be on how we work with UK supply chains, and communicate with an audience with whom we don't necessarily have strong links at the moment as we increase our business practice in adjacent markets, offering technologies originally developed for defence purposes."
The pitch currently involves nine agencies, including both Hill+Knowlton Strategies and Grayling, with an agency expected to be picked by the end of April.
Emphasising that the pitch was a reflection of Lockheed Martin moving to the "next phase of growth" rather than dissatisfaction with the incumbents, Nielson added:
"It's about finding someone who can provide innovative and creative thinking in our business-to-business and business-to-government messaging, as well as emphasising the employment and economic benefits of the business to the UK."