I think the best scenario that's possible would be for them to ignore Berlin and any other major static holdouts, simply surround them with troops to stop any major movements, and then push on into Poland and Czechoslovakia. And even for that you would need to seriously convince FDR.
I don't think that they would ignore Berlin. Its too politically important. The borders of the occupation zone may have been more or less set in stone by 1944, but the Stars and Stripes or the Union Jack flying over the Riechstag, coupled with what the KGB is telling Stalin about the Manhattan Project, would send a powerful message to the Soviets. "We chose to bail you out of your jam with the Germans, but we didn't really need to. We could have won the war by ourselves. You are the junior partner in this alliance and you owe us big time."
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