The government has asked an independent body to carry out a "detailed assessment" of the impact of EU migration as ministers look to establish the UK's post-Brexit border controls.
Home secretary Amber Rudd has asked the Migration Advisory Council to set out what impact a cut in numbers would have on the economy, including on particular regions and sectors.
And she promised there would be a transitional period to allow British businesses to adjust to the new rules.
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She said the aim was to produce a "sustainable" system which will "control the flow of immigration" but also "continue to attract people to the UK who benefit us economically, socially and culturally".
The Conservatives have committed to bringing overall net immigration down to below 100,000 people a year - well down on last year's figure of 248,000.
The committee will report back in September of next year, just six months before the end of the two-year Article 50 negotiation period.
Rudd sounded a note of reassurance to business leaders, many of whom are concerned about a drop-off in the labour supply once the UK leaves the EU.
Writing in the Financial Times, she said: "Over the past year I have heard first-hand from business leaders and employers across a range of sectors how they value European citizens for labour, skills and ideas.
"I want to reassure all those who have outlined their views, either privately or publicly, that the government is listening and that we share their desire to continue to welcome those who help make the UK such a prosperous place to live."
Rudd was also clear that there would be an implementation period for the post-Brexit immigration system, saying she wanted to "reassure businesses and EU nationals that we will ensure there is no “cliff edge” once we leave the bloc".
Business group the CBI welcomed the news, calling it a "sensible first step" towards a new set of rules.
"Workers from across Europe strengthen our businesses and help our public services run more smoothly - any new migration system should protect these benefits while restoring public confidence," it added.
Manufacturers' organisation EEF said the move showed ministers were "acknowledging that future migration changes will be implemented in a measured way over a period of years".
But the Liberal Democrats' home affairs spokesman Sir Ed Davey said the announcement had come too late.
"This will do nothing to reassure the hospitals that are already seeing record numbers of EU nurses leaving, or the companies struggling to recruit the staff they need," he said.
"The NHS, businesses and universities that depend on European citizens need answers now, not in another 14 months' time."Top of Form