DDI Corp., the country's second-largest telecommunications carrier, will launch an international telephone service today, and its low-rate approach is expected to intensify price competition among carriers.DDI, which offers international service to 235 destinations, sets its international rates for a three-minute daytime call about 30 percent lower than those offered by existing major carriers, according to a DDI spokesman. For example, a three-minute daytime call to the United States, excluding Hawaii, costs 240, 47 yen percent less than the regular fare offered by KDD.With the inexpensive rates, the carrier hopes to obtain about 10 percent of the country's international telephone service market, or 30 billion yen in annual sales by 2002.The carrier estimates that the market will shrink from the current 470 billion yen a year to about 300 billion yen a year due to the intensifying price competition, according to the spokesman.Earlier this month, Tadashi Nishimoto, president of KDD, said that his carrier would consider lowering rates or adopting additional discount rates for its international service.