General Motors announced on Thursday it will inject $117 million into its Oshawa assembly plant to build the company's all-new luxury sedan.

GM said the investment to build the new Cadillac XTS is expected to create or retain 400 jobs at the Ontario facility.

Dan Hermer, the Oshawa plant's manager, said the investment demonstrates GM's confidence in the facility.

"Having added three new products, two new shifts, and hundreds of new employees this past year, Oshawa has undergone tremendous changes," he said in a prepared statement released Thursday.

However, local Canadian Auto Workers president Chris Buckley told CTV Toronto he isn't as confident.

Buckley said the news of the investment is good but it doesn't erase the fact that GM is scheduled to move production of the popular Chevrolet Impala sedan from Oshawa to the United States.

The move, which will phase out production in Oshawa by 2013, will result in a loss of 1600 jobs, Buckley said.

"What we need to do is convince General Motors to put additional products in a consolidated plant," he said.

Buckley's measured cheer of the news was echoed by CAW president Ken Lewenza.

Lewenza told The Canadian Press on Thursday he was "delighted" with GM's decision to infuse money into the plant which will begin producing the luxury sedan in 2012 but was not certain the investment will actually translate into positions in the short term.

Lewenza said that in terms of overall job-creation, "it will really depend on the market."

Lewenza explained that usually when automakers introduce a new vehicle it generally replaces another model. Job creation would depend on increasing sales volume.

In the last year, the Oshawa GM plant has already grown considerably, welcoming 1,300 new employees to build cars like the Chevrolet Equinox and the Buick Regal.

Over 4,500 employees currently work at the plant.

With a report from CTV's Austin Delaney and files from The Canadian Press.