LONDON, Aug 18 -- British Telecommunications plc. has set its sights on German-based telecommunications operator Viag Interkom, the smallest of Germany's four mobile phone networks. British Telecom is set to acquire an additional 45 percent stake in Viag Interkom for about $6.73 billion (US), bringing its total interest in the German operator to 90 percent. British Telecom will obtain the interest via a call option sometime in 2001 from Viag Interkom's other big shareholder, Germany's E.On AG. British Telecom has also inquired about the remaining 10 percent interest in Viag Interkom with Norway's Telenor ASA, but no decisions have been made at this point.