The US ambassador to the UK said Birmingham could put its faith in Cadbury’s new owners, during his first visit to the city.

Louis B Susman said Kraft’s chief executive Irene Rosenfeld was a “personal friend” who he has known since his days as an executive banker in the firm’s home and Birmingham’s twin city of Chicago.

He said: “I think when she [Rosenfeld] says that she intends to invest in the UK and in Birmingham and maintain and extend the quality and brand of Cadbury, we can find her integrity in what she says, will happen.

“I think you will find Kraft will be a very good citizen here.”

The diplomat who visited Birmingham for two days, meeting city council leader Mike Whitby and University of Birmingham students, said he was impressed with its history and drew comparisons between the countries’ second cities.

His train trip up from London was also prompted by the Mayor of Chicago, Richard M Daley – another personal friend – who told him to improve relations between the cities.

“I’m just so delighted to be here,” he said. “I’ve heard so much about this city and really look forward to getting to know it better and to do whatever I can as US ambassador to help foster good relationships.

“One of the main reasons I wanted to come here is because we are your sister city. Mayor Daley, a personal friend, talks about it all the time. He said to me he’s very pleased with the relationship but he hopes to be able to maximise it and asked the US ambassador to do everything he could to move that along.

“I don’t think Birmingham is the second city, I don’t think Chicago is the second city. We have great attributes, both of us, and while that might be the term some might give us, I think we’re the first cities.

“We’re proud of who we are and what we are. We have great manufacturing facilities, universities, sports teams, good government and I think your weather might be a little better than ours.”

His skills in diplomacy saw him refusing to be drawn on football allegiances even though the sports-loving politician once had a hand in the St Louis Cardinals winning the World Series in 1982, as a member of the baseball club’s management.

But with the US track team heading to Birmingham for the 2012 Olympics, he said he might return to see them.

“We’re very excited that they’re going to train here and I might even come up, if I have time,” he said.

“Our Olympic committee is very pleased with selecting Birmingham as the field and track training centre. We have great facilities and the city is so welcoming to us we can’t but feel it’s the right place.”