Workers at the Greyhound bus line across Canada could walk off the job as early as Thursday after serving official strike notice Monday night in a fight for improved wages and working conditions.

The job action could affect passenger service from Vancouver to Ottawa, along with parcel and courier service. The bus line provides service to 1,200 communities.

The Amalgamated Transit Union, which represents 1,600 drivers, mechanics and baggage handlers, said the main issue in the dispute is what it calls the "Americanization" of the company.

Laidlaw International Inc., based in the Chicago suburb of Naperville, took over Greyhound Canada 10 years ago.

"We're serious now," said Jim Higgs, president of ATU local 1374, which will be in a legal strike position as of Thursday.

Higgs said Laidlaw is going to have to engage in talks with its counterpart in Canada to prevent a strike.

"It's going to take money and it's going to take a lot of working condition changes to do it. If that isn't addressed prior to midnight of that date, we're going to be out."

Higgs said working conditions have deteriorated for Canadian workers since the takeover in 1997.

The union has attempted to negotiate with Greyhound management four times since last October, he added.

Company officials could not be reached for comment.

Greyhound Canada, which has a fleet of more than 400 buses, employs more than 2,500 people across the country, including more than 375 at its head office in Calgary.

According to its website, its most frequent passengers are students, seniors and young professionals.

Its busiest terminals, based on total numbers of passengers who used its bus lines in 2004, are Toronto, Ottawa, Vancouver, Calgary, Edmonton, Winnipeg, London, Ont., Sudbury, Ont., Kelowna, B.C. and Kamloops, B.C.

With files from the Canadian Press