The UK has long had "more than its fair share" of international students, and must reconcile itself to the fact that things are going to change.
This warning was made by Richard Yelland, head of the Education Management and Infrastructure Division at the Organisation for Economic Cooperation and Development. He pointed to countries such as Japan, which plans to increase its international student body to 300,000 by 2020, to back up his point.
"The international market has always been there for some countries, but we're getting to the stage where more are realising it exists," Mr Yelland told Times Higher Education.
The UK's share of the student market may be further diminished by changes instituted after last year's review of higher education by Lord Browne of Madingley, he said.
"International students who are trying to understand the system may be thinking twice about what their options are," he said.
But Mr Yelland was positive about the UK's fees system.
"The UK should be commended for having set out to devise a system that is sustainably financed, with measures to try to improve quality and efficiency," he said.
He added that the OECD was broadly in favour of the developments in the country.
"The combination of charging a fee, providing a loan that is based on achieving a certain level of income before you pay it back, and backing it up with grants and scholarships for certain people seems to us to be the right approach," he said.
Arguing that, for tertiary education, "free is not fair", he added: "In every country of which I am aware, the upper socio-economic groups have a better rate of access to higher education than the others.
"In countries where there are no tuition fees, it is still the case that there is a bias towards socially advantaged groups."