Buildings within a 2,625-foot radius from the German construction site where the British bomb was found will be evacuated beginning 9 a.m. local time as a precaution.
It is the latest in a number of unexploded bombs found recently in Germany including one at Berlin's Tegel airport and another in Frankfurt previous year, which led to the evacuation of 65,00 people.
A number of buildings, including the Central Railway Station, Economy Ministry, Federal Intelligence Service (BND), and the Indonesia and Uzbekistan Embassies, were also evacuated.
Police say there is no immediate danger from the 1,100lb (500kg) British bomb, which was found on Heidestrasse last Wednesday.
Local bus and train routes have been disrupted during the operation while roads surrounding the station have been closed.
Police said the 100-kilogram (220-pound) Soviet bombs were found in a field in the town of Sturovo.
Earlier on Friday, the authorities said they had no idea how long the operation to defuse the bomb would take and would depend on the condition of the missile.
The operator said trains would stop at other stations in Berlin instead.
More than a million of tonnes of bombs landed in Germany during World War II and more than one tenth thought to be unexploded.
Past year some 60,000 people were evacuated from their homes in Frankfurt after a massive bomb dropped by Britain's Royal Air Force was unearthed.
Flights to and from Tegel airport - about 7km away - were not affected by the evacuation.
The bomb defusing team talks with media next to dismantled World War II bomb at a construction site near the central train station in Berlin, Germany, April 20, 2018.