Europe’s leaders need to send a much stronger message that they will no longer offer “refuge and support” to migrants if they want to curb the right-wing populism spreading across the Continent, Hillary Clinton warned in an interview published Thursday.

Mrs. Clinton said that while the decision of some nations to welcome migrants was admirable, it had opened the door to political turmoil, the rise of the right and Britain’s decision to withdraw from the European Union.

“I think Europe needs to get a handle on migration because that is what lit the flame,” Mrs. Clinton said in the interview with The Guardian, which was conducted before the United States midterm elections this month.

“I admire the very generous and compassionate approaches that were taken particularly by leaders like Angela Merkel, but I think it is fair to say Europe has done its part, and must send a very clear message — ‘we are not going to be able to continue provide refuge and support’ — because if we don’t deal with the migration issue it will continue to roil the body politic,” she said.