Major League Baseball is close to a tentative agreement with the city that would clear the way for a new stadium for the Washington Nationals and the long-awaited sale of the team. D.C. Council Chair Linda W. Cropp said Saturday on WRC-TV that a deal had been reached with baseball agreeing to contribute $20 million to a contingency fund and guarantee rent payments. However, a spokesman for Mayor Anthony A. Williams said talks between city officials and baseball are still being held this weekend in Washington. "We're just not there yet. There are some people who feel a little more confident in saying," spokesman Vince Morris said. "I'd rather have it hand before I claim that we've got a deal."