LONDON  In the face of mounting concern about abuse of student visa rules by migrant jobseekers and potential terrorists, Britain said Sunday that it was planning an immediate tightening of its border controls that could reduce the flow of people entering the country as students by tens of thousands a year.

The new rules will apply to all applicants from outside the European Union, including the United States. But the primary focus appeared likely to be the Indian subcontinent and countries in the Arab and Muslim world, both because of the large numbers of allegedly fake applicants who originate there and because of concerns about combating terrorism by Islamic extremists.

The controls appeared to have been drawn up, in part, to meet American pressure for a tougher British approach to combating terrorist threats. While officials from both countries say counterterrorism cooperation has been close, United States officials have warned that Britain, with its large Muslim population and its relatively open borders, is among the countries that are central to American concerns as potential planning grounds for terrorist attacks against the United States.

Announcement of the new controls came six weeks after the failed attempt on Christmas Day to bomb an American airliner approaching Detroit on a trans-Atlantic flight. The 23-year-old Nigerian charged in that attack, Umar Farouk Abdulmutallab, spent three years in Britain as an engineering student and while in London associated with radical Muslim groups, though British and American intelligence officials have said he was prepared for the bombing attempt by associates of Al Qaeda in Yemen.