Theresa May will meet major US investors in New York in an attempt to reassure them about the Brexit process.
The Prime Minister is among the world leaders who have arrived in the US city for the United Nations General Assembly (UNGA) amid tight security following the bomb attack in the Chelsea district of Manhattan.
She will take part in a high-level summit on the migrant crisis, where she is pressing for a recognition that countries have the right to control their own borders, and a better distinction between genuine refugees and people moving for economic reasons.
But Mrs May will also take the opportunity to meet key US businesses with investments in the UK, in an effort to allay their concerns.
She said she would meet "business leaders here in the US" to "keep businesses investing in the UK in key sectors".
During her visit to New York Mrs May will meet Japanese prime minister Shinzo Abe for talks on Tuesday, just weeks after his government produced a 15-page dossier listing his country's firms' concerns over Brexit.
Mrs May will host a round-table event for major US investors from industries ranging from banking to entertainment.
Firms represented at the event will include Goldman Sachs, Morgan Stanley and Amazon.
She will also attend a reception for firms from both the UK and US that are engaged in transatlantic trade.
"What I will be talking about with both American and British business leaders is about how we can encourage that trade and investment between the two countries," Mrs May told reporters on the RAF Voyager taking her to New York.
"Something like a million people in the UK wake up each morning and go to work for an American company in the UK.
"I will be talking to them and hearing from them what their emphasis is in terms of the issues that they want us to address, but when we go into the negotiations for the trading deal with the European Union that will pertain once we have left the EU, we will be aiming to get the right deal for the UK."
That "ambitious" deal would cover both goods and services, she insisted.
Mrs May set out four priorities for her first UNGA as prime minister.
"The first is on migration, where I want to encourage a better global approach to better managing migration flows throughout the world.
"The second is on Syria, and that's going to be around securing more and better humanitarian support for those who are in need in Syria.
"On aviation security, we are looking to strengthen international efforts on aviation security.
"We have put forward a resolution to the security council, I think it's the first time it's had a resolution on aviation security, which we hope is going to be supported later this week.
"Finally, on modern slavery I want to raise awareness of the need for us to be working internationally to deal with this terrible crime of modern slavery that takes place across the world.
"Those are the priorities for UNGA itself, but outside of that there will be opportunities - I will be meeting various leaders from Pakistan, Japan, Egypt, Turkey among others."
Ahead of the summit, Mrs May said that refugees should claim asylum in the first safe country they reach and stressed that nations have a right to control their borders and a responsibility to prevent illegal and uncontrolled migration.
She defended the UK's actions on helping refugees fleeing the conflict in Syria.
She told reporters on the plane: "We have always taken the view in relation to helping Syrian refugess that, actually, we can help all Syrian refugees by putting aid into the region. We are the second biggest humanitarian donor, we have a very proud record - there will be Syrian children being educated, people with medical supplies, with water, with food, as a result of the efforts that the UK taxpayer has put in through our donations.
"We are taking the 20,000 from the Syrian vulnerable persons relocation scheme but we also are taking Syrians in through other routes as well - through the normal asylum seeking route, (and) we are taking 3,000 vulnerable children from the region, some of whom will be Syrian, some will not be."