The next-generation Chevrolet Cruze.[Photo/Reuters]

Detroit - General Motors Co has delayed the launch of the next-generation Chevrolet Cruze by a year due to engineering changes and a desire to squeeze more sales from the small car before it is redesigned, people familiar with the US automaker's plans said.

The next version of the Cruze, which had originally been scheduled to debut in late 2014, will now begin production in December 2015, said the sources, most of whom asked not to be identified in discussing GM's plans.

Canadian Auto Workers union leaders at a supplier plant in Stratford, Ontario, have already announced the delay to members.

The automaker has said the next Cruze will be completely redesigned inside and out, with a larger trunk and roomier passenger compartment, and will get better fuel economy.

In the first six months of the year, US sales of the Cruze were up 17 percent to almost 134,000, and in June it ranked as the second-best selling passenger car behind only Toyota Motor Corp's mid-sized Camry.

The Cruze was first introduced in 2009, the year GM came out of bankruptcy with the help of a $50 billion US taxpayer bailout. However, by the end of 2013 - as GM finishes rolling out several new vehicles - the Cruze will be the company's oldest model.