Microblogging serviceTwitter is preparing to open its first office outside the United States, with company representatives meeting with London property agents last week, according to British newspaper The Telegraph.

The San Francisco startup is already an international service in the sense that it has a growing user base outside the US. (That was a major reason Twitter struggled to deal with the heavy usage brought on by the World Cup.)

But just as the company is finally starting to launch ad services in the United States, it’s preparing to make money from that international audience too. The Telegraph says the new office will be used primarily for sales and that it will be led by former Googler and White House staffer Katie Jacobs Stanton.

The company reportedly commented, “There were a few of us in London this week. We are considering London and other European locations to create an initial and small presence in 2011.” I’ve emailed Twitter for additional details and will update if I hear back.

[photo via Flickr/Dimitry B]