SEOUL (Reuters) - South Korea's economy faces downside risks as the U.S. Federal Reserve gears up to raise interest rates and Korea overhauls of its shipping and shipbuilding industries, the finance ministry said on Thursday.

The ministry noted in its monthly assessment of the economy that growth could be constrained by extensive strikes at automakers.

Unionized workers at South Korea's Hyundai Motor <005380.KS> rejected a tentative wage deal last month, signaling more strikes and production losses at its biggest manufacturing base.

August export data showed early this month shipments would have performed better had it not been for the auto strikes.

The ministry statement said domestic consumption was adjusting to the expiry of some favorable government measures such as tax breaks.

(Reporting by Christine Kim; Editing by Eric Meijer)