In an announcement today, the Guardian revealed that Gibson will relocate to New York along with guardian.co.uk news editor Stuart Millar, who will be deputy editor of the new operation.
Earlier this week the Guardian declined to comment further on a report by Yahoo media blog the Cutline that it was building a new US digital operation "significantly larger" than its previous work in the states.
In a release announcing the plans today, Gibson said: "We're immensely proud of guardian.co.uk and how its global audience has grown, especially with our coverage of WikiLeaks and the Middle East over the last few months.
"We've learned a lot about what digital journalism can do, and now we want to build on that to cover America better and cover the world better for our American users. To do that, we'll be mixing the journalistic ambition, trust and long history of the Guardian with the energy and innovation that comes from being a start-up in the world capital of digital media."
According to the Guardian it has an audience of around eight million unique users in the US, based on statistics from Comscore for February 2011.
The latest report from the Audit Bureau of Circulations, also for February, claims that 60 per cent of traffic to guardian.co.uk is from outside the UK.
"The Guardian, which is owned by the Scott Trust, has attracted a very considerable audience in America in recent years," Alan Rusbridger, editor-in-chief of Guardian News & Media, said in the release.
"We believe there is real demand for the sort of open, internationalist, digital journalism which we have been pioneering. Janine Gibson has been at the heart of our web operations and is the ideal person to lead our new team in the US."