OTTAWA, Aug 18 (Reuters) - Canadian National Railway ( CNI )

, one of Canada's two main rail companies, formally

notified the Teamsters union in Canada on Sunday that it would

start locking out union workers early on Thursday.

"Unless there is an immediate and definite resolution to the

labour conflict, CN will have no choice but to continue the

phased and progressive shutdown of its network which would

culminate in a lockout," it said in a statement.

"Despite negotiations over the weekend, no meaningful

progress has occurred, and the parties remain very far apart."

Canada's other main rail operator, Canadian Pacific Kansas

City ( CP ), has already told the Teamsters union it will start

locking out members early on Thursday. This means the vast

majority of rail transit of goods in Canada would grind to a

halt by Thursday, barring last-minute labour agreements between

the companies and their respective arms of the Teamsters' union.

Separately, Teamsters also issued a 72-hour strike

notice to CPKC late on Sunday.

"Unless parties reach last-minute agreements, a work

stoppage will occur at 00:01 on Thursday, August 22," it said in

a statement.

The companies and the union accuse each other of bad

faith in the talks. The teamsters say CN Rail and CPKC are

seeking concessions that could endanger worker safety, a charge

both the operators deny.

The federal Liberal government has so far dismissed

pleas from business groups to intervene, saying it wants the

companies and the union to sort out their differences via

negotiations.