Homeland Security Secretary Janet Napolitano warned Monday that her agency would be forced to furlough 5,000 border control agents under mandatory spending cuts, likely allowing more illegal immigrants into the country and potentially compromising national security.

Napolitano said the cuts, known as the sequester, would disrupt the Department of Homeland Security’s ability to conduct customs inspections at ports, leading to increased waiting times for travelers and cargo shipments. Disaster relief funding would be reduced by $1 billion, she added, meaning relief for victims of natural disasters like Hurricane Sandy and tornados in Joplin, Mo., and Tuscaloosa, Ala., could be cut.