(Recasts with dropping plans to seat Franken on Tuesday)

By Thomas Ferraro

WASHINGTON, Jan 5 (Reuters) - Senate Majority Leader Harry Reid yielded to Republican threats and agreed on Monday not to immediately seat fellow Democrat Al Franken, whose razor-close victory in Minnesota faces legal challenges.

Senate Republicans had planned to disrupt the opening of the new Congress on Tuesday by blocking Franken's swearing-in.

And in another ugly fight, Senate Democrats vowed to block, at least for now, the seating of fellow party member Roland Burris whose appointment by embattled Illinois Gov. Rod Blagojevich carries a whiff of political scandal.

The 57-year old Franken, who gained fame as a writer and performer on the satiric Saturday Night Live television show, on Monday officially was declared the victor by a 225-vote margin by Minnesota state officials from nearly 2.9 million votes cast.

But lawyers for incumbent Republican Norm Coleman complained the recount was conducted unfairly and promised a court challenge that could take weeks to resolve.

"Shortly after Election Day, Coleman criticized Mr. Franken for wanting a recount and wasting taxpayer money. Now that it is clear he lost, Coleman should follow his own advice and not subject the people of Minnesota to a costly legal battle," Jim Manley, spokesman for Reid of Nevada, said in a statement.

"However, there will not be an effort to seat Mr. Franken tomorrow," Manley said.