The Secretary of State has insisted he will have a "loud voice at Westminster" in speaking up for Northern Ireland in the Brexit talks.
ames Brokenshire restated the Government's position that it does not want to see a return to a hard border with the Republic, featuring security and customs checks.
And he pledged that any move to limit the number of foreign workers employed by local firms would be "careful, thoughtful and measured".
Mr Brokenshire has been touring Northern Ireland since his appointment in July, meeting business owners, farmers and lobby groups.
He conceded that they have expressed deep concerns about how the border will look after the United Kingdom leaves the European Union and how their employees will be affected.
"I hear that anxiety, that sense of the importance of not seeing a return to hard borders, borders of the past," he said. "There will be challenges ahead, but I have a sense of optimism for the best outcome.
"There's a really strong political will between ourselves, as the UK Government, the Executive and the Irish Government.
"None of us want to see a return to hard land borders and the benefit we get from the common travel area."
Earlier this week, at the Conservative Party Conference in Manchester, the Home secretary Amber Rudd caused controversy when she suggested that employers may be compelled to disclose how many foreign workers they employ, with business leaders describing it as divisive and damaging.
Some Northern Ireland firms, like Moy Park, employ significant numbers of migrant workers. And many companies have staff who are resident in the Republic.
"There's a need for greater control on immigration because the levels we've seen since 1998 are not sustainable in the long term," said Mr Brokenshire, who previously dealt with immigration policy as a Home Office Minister.
"Free movement as it exists now in relation to EU citizens can't continue. It's about looking at this thoughtfully, but equally recognising the huge contribution that EU citizens make to our economy, culture and society."