The biggest U.S. automaker, General Motors, has announced it will boost production by 60,000 vehicles in response to rising sales, a result of the government's Cash for Clunkers program.

GM said Tuesday it is adding shifts at plants in Canada and the U.S., bringing some 1,350 laid-off employees back to work.

Analysts say rising sales have contributed to a shortage of the most sought-after car models.

GM emerged from bankruptcy last month.

Ford Motor Company also has announced it will increase production in response to brisk sales for its Ford Focus and Escape models.

Cash for Clunkers gives car owners up to $4,500 in rebates to trade in older, gas-guzzling vehicles for newer, more fuel-efficient models.

Some information for this report was provided by AP, Bloomberg and Reuters.