Theresa May has insisted that Brexit will result in the "best possible" trade deal with the European Union in an effort to reassure nervous US financial giants.
The Prime Minister hosted a meeting with major US firms, including some of Wall Street's biggest names, while in New York for the United Nations General Assembly amid concerns that they could shift their operations from the UK to elsewhere in Europe.
Mrs May said she recognised their concerns and wanted to ensure that financial services would be covered by the Brexit deal.
Under passporting arrangements, financial firms with headquarters in one EU nation can operate across the bloc - but Brexit could put the City of London's status at risk.
In an interview to be broadcast on Wednesday's Morning Edition on National Public Radio in the US, Mrs May said: "One of the purposes of my meeting with US investors, and that included US banks, was to hear from them what their concerns are and what their key issues are as we go forward for our negotiations.
"And I was able, I hope, to reassure them that I want to ensure the best possible deal for the UK in trade with the European Union, not just in goods but in services.
"I hope the message they took was that I recognise the importance of financial services and the City of London as an important international financial centre."
Mrs May is ambitious for a trade deal with the United States, despite Barack Obama's view that he would prefer to focus on the proposed EU agreement.
She said: "There's a limit to what we can formally sign up to while we are still members of the European Union, and obviously, one of our negotiations is going to be our trade relationship with the EU, but I'm very clear, and I've been talking to leaders. I've talked to President Obama.
"I've talked to other leaders around the world, and there is a real interest in ensuring that we can develop the economic and trading relationships between the UK and a number of other countries including the United States."
She acknowledged that concern about migration was one of the key drivers for the Brexit vote.
Mrs May said: "I think what people were voting for was a feeling of more control in a number of areas over their own lives, more control, for example by the British government over who could come into the United Kingdom.
"You have those controls here in America, an ability to decide who can come over and work in America, for example, so I think people wanted to see more control for the British Government, and that was one of the issues."
She added: "The vote was clearly a vote that people wanted us to bring control into the movement of people from the European Union into the United Kingdom, but if I may, I haven't said in specific terms exactly what trade deal we want with the European Union once we have left, and there are a number of models at the moment.
"Norway has a relationship with the EU which involves the free movement of people but also access to the single market. What I want is for the United Kingdom to be able to forge its own relationship with the European Union. We're looking for that new relationship."
Mrs May also defended Foreign Secretary Boris Johnson, who was given a rough ride by the US press in July over his past comments about Mr Obama and Hillary Clinton, saying he was doing an "excellent job".