The South Korean won ended

The South Korean won ended 3% higher Monday to close at a one-month high as offshore market participants dumped the dollar to track regional-market trends, dealers said.   The big question now on everyone's mind is whether the won can sustain its gains, with traders saying that Wall Street's performance will likely hold the key to the domestic currency's fortunes.   The dollar rose to a high of KRW1,488 in early trade, but reversed course to close at its weakest since Feb. 16, when it had closed at KRW1,427.50.   "There appears to have been some offshore players betting on a short-JPY/KRW position by buying the dollar versus the yen and simultaneously selling the dollar against the won," a local bank trader said.   On Tuesday, traders say that market participants will keenly watch whether the dollar will recover support at KRW1,450.   Domestic treasury bonds ended a tad lower following weak results at an auction for KRW800 billion worth of 10-year treasury bonds, which were sold at 4.97%, compared with their close Friday of 4.88%.   The country's chief financial regulator said Monday that money market funds will be required to diversify their holdings into bonds and commercial paper later this year.   These funds must invest at least 40% of their assets in bonds and commercial paper, the Financial Services Commission said in a statement. Funds will be allowed to invest at most 5% of their assets in treasury bonds with maturities ranging from one to five years.   Revising rules to allow investments in long-term securities is a bond-friendly move, but the impact will be likely limited, analysts said.   Money-market funds have frequent deposits and retrievals, and as such, "fund mangers would be reluctant to invest in instruments with such long maturities as five-year treasuries," said Woori Investment & Securities analyst Ough Chang-sup.