* Overall investors yet seem cautious about KOSPI -analyst * Won steady; Fed chair Janet Yellen's testimony eyed SEOUL, July 11 (Reuters) - South Korean shares rose early on Tuesday led by gains in large- cap shares, while investors cautiously awaited second-quarter earnings guidance from other companies. The Korea Composite Stock Price Index (KOSPI) was up 0.4 percent at 2,391.71 points as of 0227 GMT. Steelmaker Posco was up over 2 percent while web portal Naver Corp climbed 2.5 percent. However, overall trading seems to be slow as market participants are still uncertain about how much the KOSPI could gain in coming quarters, said Kim Hyung-ryeol, a stock analyst at Kyobo Securities. "Forecasts for sectors other than IT are not that optimistic, making market participants think twice about investing more." Offshore investors were poised to be net sellers, offloading 18.2 billion Korean won ($15.85 million) worth of KOSPI shares. Advancers outnumbered decliners 417 to 367. The South Korean won also tread water, awaiting Federal Reserve chair Janet Yellen's testimony in Congress on Wednesday and Thursday. The won edged up 0.1 percent at 1,148.9 against the dollar versus previous close at 1,149.5. September futures on three-year treasury bonds shed 0.02 point to 109.14. 0227 GMT Prev close Dollar/won 1,148.9 1,149.5 Yen/won 10.0640/10 10.0699 *KTB futures 109.14 109.16 KOSPI 2,391.71 2,382.10 * Front-month futures on three-year treasury bonds (Reporting by Dahee Kim; Editing by Sunil Nair)