The transport giant, under pressure to drive through changes from 9.8 per cent shareholder Coast Capital, could also review its train franchises as it looks to focus on its student and shuttle bus services across the Atlantic, for which it sees significant long-term potential.
Its new direction was unveiled alongside an annual £97.9million loss despite growing revenue by 11.4 per cent to £7.12billion.
It took a £102.1millon hit from future loss on its South Western Railway franchise, as well as impairments in First Bus.
Adjusted operating profit at Greyhound, which has faced increased competition from low-cost airlines and increased car use, fell 55.3 per cent to £11.4million.
The group has concerns over the future of its rail division, which includes Great Western Railway and TransPennine Express.
Rival Stagecoach has launched legal action against the Department for Transport after being barred from bidding for franchises amid a row over staff pension contributions.
FirstGroup chief executive, Matthew Gregory, said: “Any future commitments to UK rail will need to have an appropriate balance of potential risks and rewards for our shareholders.
Its First Bus arm carries about 1.6 million passengers a day, with a fifth of the market outside London and a fleet of about 5,800 buses.
Gregory said: “First Bus has limited synergies with our other operations”
AJ Bell investment director, Russ Mould, said: “It looks like the commitment to rail is wavering. This leaves just US school buses and private transit operations in the States, suggesting FirstGroup believes the best businesses come in smaller packages.”
Shares rose 4p to 114½p.