China's economy "hit bottom" by late September, but a rebound by the end of this year isn't out of the question, economist Stephen Roach said.

The former non-executive chairman of Morgan Stanley in Asia also said he expects China to maintain an annual economic growth rate of about 8 percent - half a percentage point above the 2013 target set by former premier Wen Jiabao last week.

"The economy seems to have hit bottom in the third quarter (of 2012), and I expect progressive strengthening over the course of the year - especially if the external climate starts to improve on the heels of a gradual pickup in global growth," Roach told China Daily.