OTTAWA - Back-to-work legislation from the feds could soon derail the Canadian Pacific Railway strike.

Labour Minister Lisa Raitt has said the government is prepared to roll out the legislation as soon as Monday if CP and the union representing striking employees can't strike a deal.

In a Sunday interview, Raitt told CTV's Question Period that talks between the union and CP rail have become "more difficult" but the government hasn't lost faith in the negotiations.

"As it becomes more and more apparent the effects on CP, the company, of the strike, things are getting more difficult at the table," Raitt said. "I'm still hopeful."

About 4,800 members of the Teamsters Canada Rail Conference, including CP rail engineers and conductors, walked off the job Wednesday after talks broke down over pension issues and work rules.

The strike has shutdown freight traffic across the country and Via Rail cannot operate on tracks where CP is the host railway.

Last week, Raitt said she was concerned about the economic impact of the strike because the government estimates it could cost $540 million per week.

"There is no intervention at this point in time," Raitt told reporters Wednesday. "That being said, there is a point in time when a person's right to strike is measured and it is balanced against the national economy and the best interests of the Canadian public."

The Conservative government has recently used back-to-work legislation to end disputes at Air Canada and Canada Post despite outrage from opposition parties.

The NDP says the government's threat of back-to-work legislation provides companies the upper hand in negotiations because workers will ultimately be forced to return to their jobs.