UPDATE 2-South Korean Sept exports fall, rising won a worry

(Recasts with production data, updates markets)

By Cheon Jong-woo and Yoo Choonsik

SEOUL, Oct 1 (Reuters) - South Korea posted an unexpected fall in September exports on Monday, marking the first annual decline in more than five years, but analysts were confident exports would remain resilient despite a slowing U.S. economy.

The Bank of Korea, however, sounded a warning it would closely monitor currency movements, as the won rose to a two-month high, reflecting growing official unease a strong currency would hurt the country's export competitiveness.

The outlook of South Korean companies, who have for years tried to reduce their reliance on the United States, had also not been badly affected by a slowing U.S. economy, surveys showed.

Analysts and investors anticipated Asia's fourth-largest economy would remain on an accelerating growth track, although firmer oil prices and the resurgent won were now emerging as fresh hurdles for the heavily energy-dependent economy.

"The proportion of South Korean exports to the U.S. has been declining against our total exports in the past few years, while exports to emerging markets have been rising because those countries have got richer thanks to higher raw material prices," said Jun Min-kyoo, an analyst at Korea Investment & Securities.

"Taking account of this, the impact of a slow U.S. economy will not be as big as has been expected."

Exports in September fell 0.4 percent from a year earlier and imports also slid 2.1 percent, Commerce Ministry data showed, hit largely by the three-day Thanksgiving holidays which this year all fell in September. The holidays can also fall in October.