Washington, D.C. ? A high-stakes battle over who will gain control of the nation’s fourth-largest bank intensified over the weekend, with the Federal Reserve acting as a go-between in the pursuit of Wachovia by both Citigroup and Wells Fargo.

Wachovia agreed Friday to be bought by Wells Fargo, spurning Citigroup, which had agreed to buy most of the troubled bank a few days earlier. As Citigroup and Wells Fargo mounted aggressive legal battles for Wachovia, the Fed stepped in to try to broker a compromise that would eliminate uncertainty over the future of the Charlotte, N.C.-based bank.

One possibility that emerged in the talks with the Fed was that part of Wachovia would go to Citigroup and part to Wells Fargo.

Even as those conversations were occurring, an epic legal battle was shaping up. A New York judge late Saturday night issued an order that Citigroup said suspended Wells Fargo’s deal for Wachovia on the grounds that Wachovia already had betrothed itself to Citigroup and was not allowed to talk with other suitors. But on Sunday evening, a New York state superior court blocked the Saturday ruling, leaving the legal issues unresolved pending further hearings.

Meanwhile, Wachovia filed a federal lawsuit Sunday seeking affirmation of its right to accept Wells Fargo’s offer. U.S. District Court Judge John Koeltl gave the sides until today to file arguments.