Via Rail says it could cancel passenger service from Quebec to the Maritimes if CN doesn't find an investor to buy a portion of its railway in northern New Brunswick.
CN announced last week that it will discontinue operations on a 70-kilometre section connecting Bathurst to Miramichi because their freight cars don't use the line.
Via Rail's Ocean line runs on the same route.
Spokesperson Mylène Bélanger said Via Rail will maintain the connection between Quebec and Halifax for as long as it can, but will not acquire the railway itself.
"At this time it's still a hypothetical question, but if this section is abandoned we'll look into the commercial viability of all other alternatives, for connecting between Halifax and Montreal, before adopting any other route," she said.
CN said operations will be maintained on the tracks between Nelson Junction and Nepisiquit Junction for at least five months while the rail line is put up for sale.
"Via Rail does not have the financial resources to acquire or maintain this section of the tracks. So we'll wait for any developments," said Bélanger.
Daily passenger train service in the Maritimes was scaled back to three days a week in October 2012.