The president will personally lead a Sept. 22 meeting of the U.N. Security Council focused on the threat posed by foreign terrorist fighters, and the U.S. will seek a new resolution demanding countries tighten laws to prevent the flow of fresh recruits to terror groups.

It has emerged as a major security concern as possibly tens of thousands of individuals have gone to Syria to join ISIS, including over a thousand from Europe who would be eligible to travel back to the U.S. without a visa.

Defense Secretary Chuck Hagel recently said that more than 100 U.S. citizens with passports are fighting alongside the terrorist organization in the Middle East. Thousands more are suspected of joining ISIS from other European countries.

The resolution “will increase the obligations on states to try to prevent and deter the flow of foreign fighters,” National Security Adviser Susan Rice said Friday.

“It will move the ball down the field in terms of the international legal architecture and obligations on states to try to combat this challenge,” she added.