More than half of large US companies operating in the UK plan to increase investment in the next few years, even though they are concerned about the lack of Trade agreements between countries with Britain withdraws from the European Union.

A survey of 68 large American companies employing more than 275,000 employees in the UK found that the country is “very high” as a place to do business. About one-third of people believe that confidence is at the highest level, while about 60% said they will increase their investment in the UK.

The survey was conducted by the American/British trade association BritishAmerican Business and consulting firm Bain, and covered businesses ranging from financial services and manufacturing to technology, media and telecommunications. Respondents included insurance company Marsh McLennan and payment company American Express.

Anna Mars, President of American Express Group, said: “The strong multilingual talent base, favorable business environment, and geographical and time zone advantages continue to make the UK an ideal starting point for our business outside the United States.”

Dan Glaser, President and CEO of Marsh McLennan, is equally optimistic. “The UK is a large and dynamic economy with an excellent regulatory and education system,” he said. “Top talents from all over the world want to work and live in the UK.”

However, the investigation also found that there are concerns about Brexit and US trade relations among American companies with large-scale operations in the UK.

The main concerns about Brexit are the risks of political tensions and practical issues such as supply chain issues and the ability to obtain talent from the EU. Regulatory barriers, loss of ability to perform certain services in the EU, and tariffs have also been flagged.

Approximately 17% of US companies surveyed stated that they have moved jobs to the European Union.

The US companies surveyed warned that these Brexit worries may obscure their future prospects, and the survey plans to become an annual indicator of US investment intentions in the UK.

Nearly 40% of companies stated that the first priority should be to improve political and economic relations with the European Union so that the UK maintains its prime position as a US investment destination.

“The UK is in a good position to continue to attract companies from the US and around the world,” said Duncan Edwards, chief executive of BritishAmerican Business.

“But reaching a comprehensive trade agreement with the United States, establishing a more active political and trade relationship with the European Union, and a more business-friendly domestic policy will enhance this positive outlook.”

The survey revealed that another important priority for US companies is the completion of trade agreement negotiations between Washington and London. According to people familiar with the matter, International Trade Secretary Liz Truss will travel to the United States this week to meet with officials.

Other suggestions to the British government include clearing up its industrial strategy and maintaining a corporate tax environment conducive to business.

Jonathan Frick, a partner at Bain in London, said that since the United Kingdom withdrew from the European Union, American investors have retained most of the workforce. “In particular, financial services companies believe that the city will continue to be a business center with a broad and diverse talent pool,” he said.