Many U.S. tennis fans were frustrated Friday upon discovering that Roger Federer's victory in the French Open semifinals was not available on live TV in this country. The reason: arcane rules governing the televising of the semis, one of which was to be seen on NBC, the other on the Tennis Channel. NBC's broadcast window is from 10 a.m. to 1 p.m., so it opted for the earlier semi, which Open officials designated for Robin Soderling against Fernando Gonzalez. NBC showed it on a delay. That left Tennis Channel to show Federer vs. Juan Martin del Potro, but not until 4 p.m. Eastern time; NBC's window of exclusivity is for 10 to 1 in every U.S. time zone. A wrinkle nearly landed Federer on live after all. Tennis Channel offered to trade matches with NBC if the early semi ended before 10 a.m., which would have landed Federer live in NBC's window - at least in the East. But once the Soderling-Gonzalez match ran to 10:45 and NBC began to show it, the opportunity for a switch became unavailable. The men's final will be shown live Sunday morning at 9. -- NEIL BEST